Betcha' the stock system without anybody's changes will cool a Chevy engine just fine...provided it is in good condition, and provided all of the ancillary items such as shrouds and other items that affect the airflow into and out of the engine compartment, are present.
I know this is an older post but wanted to address it just the same.
Well gm's clutch fan setup in stock config & stock setup doesnt cool near as well which is why i did all the testing etc to come up with a better modified version of gm's base clutch fan cooling setup & why my rec upgraded clutch fan setup cools better with a lot of 1st hand testimonials for your fellow t/c members in their own words backing up everything i say when they do everything i rec and heres what i do that makes gm's clutch fan setup cool considerably better by 25-30 deg on avg on a hot summer day.
The items below is what i do to chevelles that already have the stock shroud and stock 7 blade 772 type gm clutch fan used for ac/hd cooling apps along with a hd cooling 4 row stock type rad from ground up or a Dewitts hi perf AL rad for given app.
I also include some tuning /timing tips to reduce engine temp too esp when running a non stock non gm type aftermarket perf cam.
* seal the lrg airgap between rad core and shroud ,doing that makes all air moved/sucked by clutch fan actually bpases thru rad core for max cooling vs sucking x-amount of heat underhood air thru the lrg airgap between shroud and rad core that most chevy's had.
* install autozones hi flow 15356/160 stat that is an important parts of the combo i rec that keeps bbc at 180 deg +- few dag all day ong in 90-95 deg outside temp vs GM rec 190-195 stat to make motor & ex gases run hotter to reduce certain ex emissions & not to help it perf better.
The old school sbc/bbc non emmission motors of 40+ yrs ago run better on street at approx 180 deg + - few deg (in head temp) vs 200+ when running the rec 190-195 stat gm rec from mid to late 60's on up.
* install a hd hayden thermal fan clutch that locks up for little more fan rpm which increases cooling vs stock repl std duty thermal fan clutch that doesnt lock up a much resulting in less fan rpm = less air being sucked/moved thru rad core so less cooling.
* have the original w-pump rblt re-using the stock for back in the 60's-early 70's better flowing/pumping cast iron impeller with closed back or a new cast iron hi flow pump from milodon or summit with same type better flowing impeller vs a new std repl pump or rbly pump using a new type inferior pumping cookie cutter ;looking stamped steel impeller with open back relying on very precise backplate to impeller clearance to get decent pumping which unfortuantely i found to not always be the case significantly reducing pumping/flow efficiency of the pump.
* with any kind of non gm aftermarket perf cam you need to run a lot more base timing very mild cam 16-18 deg base timing,hotter cam 18-20 deg base timing.
Note,must set base timing with max of 550-600rpm idle speed to ensure mech adv in dist isnt adding additional timing to base timing setting.
* also,if dist has a vac adv have it limited to 10-12 deg max using crane cams vac adv limiter plate, Try full vac all the time as long as theres enough idle vac to keep/hold vac adv at its fully deployed position for max timing at idle (in gear with auto trans) .
If theres not enough vac at idle to hld vac adv fully deployed all the time it can lead to unstable idle speed and if thats the case move vac adv to ported vac to vac adv is only used when throttle is above idle circut.
an old school non emission sbc/bbc street perf motor can really benefit from a vac adv if at all possible to do so.
* ensure motors getting all the octane it needs too because todays pump is formulated a lot different for latest gen emission motors along with ethenol too which makes you have to 1st of all jet one jet larger /sometimes 2 to get proper AFR due to diff todays formula non leaded pump fuel with 10% ethenol added.
and if the motor could benefit from some additional octane that can make it run cooler when the motor gets the additional octane it needs .
Heres a link to the proper real lead if you want to try & see if your motor responds well to some additional octane.
Bottom lines is if you do all the above (everything) just as i rec using same mfg's part-s i rec along with my tuning/timing rec your old school non emission sbc/bbc street perf motor will run 180 deg + - few deg all day long in 90-95 deg outside airtemp heat.
Running the old school sbc/bbc motors at 178-180 deg like my rec setup does (vs 200-205+ with gm's stock clutch fan setup using their rec 190-195 deg std flow stat) and the motor running a lower temp reduces it's octane requirement too!
I attached a chart that shows octane requirement taking into acct we are using todays different formula non leaded lower octane pump fuel with 105 ethenol added which i found to be very accurate when talking old school muscle cars motors with higher comp and short cam timing for higher cyl pressure or with mild perf cams still keeping cyl pressure higher.
When you get away with lower octane fuel with 10-11.0 comp old school motor with no detonation is when you have stall converter & more gear like 3.73-4.10 reducing load on motor,,dont use vad adv removing min of 10-12 deg timing from the motor,also many guys dont run enough base timing with perf cams and only set timing for total only which leaves base timing very retarded like approx 8-10 deg on avg too (so between no vac adv and retarded base timing thats a total of approx 18-22 deg timing thats removed from the motor which is huge in aking it not detonate on lower octane pump fuel),maybe even al intake or al heads reducing engine/comb chamber heat making it less likely to detonate too is when pumps fuel isnt an issue.
so hopefully the engine temp vs compression vs octane requirement chart thats taking into consideration toadys diff pump fuel chart cam thru/attached ok for you to chk out.