Having a BB and 3:08 gears I want better low end.
It's come to change in transmission gearing or rear end gearing.

one solution is to get the new gear set for Muncies that have a 2:98 first gear an better 2nd gear and then leaning back to regular 3rd and then 3:08 gearing.
Problems I see with this:
cost
what do you do about the speedometer ?
case is longer and may or may not be a problem for driveshaft.
gear shift handle may or may not be a problem with people with consoles.
down time as I would have to ship transmission out for install of new gears.

second solution is the 3:42 gear swap.
less cost
less down time
speedometer can be calibrated
local expert for gear installation
decent gear for highway

Have I answered my own question ?
Thanks.

any muncie will be 1:1 in 4th gear so going to a lower first gear won't affect the current speedometer read out.

Speedo doesnt get recal for rear gear swap,theres a small driven gear that accessable from outside trans that needs to be replaced ,generally takes 15 mins to do from under car if speedo gear pod isnt stuck in trans like can happen from time to time.

That small driven speedo gear is avail on ebay/ on the web at many muncie rebuilder sites/or a gm dealer with proper pt#.

I would go with either either used or nos 3.31 with bbc or new 3.42's & little taller tire like 26.5 maybe 27"

I went from 307 gear to 331's in my 69 with m20 (all muncies have same 1 to 1 4th gear final ratio) along with 25.5-26" tall tires & it turns approx 2,650rpms @ 60mph & approx 2950 rpms @ 70mph).

Even that relatively small gear swap gave me a nice increase un te BUTTOMETER perf scale/LOL!!!!

So you going from 308 to 342 would be a little better but cruise rpms would be slightly higher by approx 100rpms max.

331-342 gear is about the best comprimise between perf & resonable cruise rpm your ever going to get esp for a bbc without going to OD trans /tremec 5spd/or very tall stupid looking tires.

The gear swap will be approx 3x cheaper then going with a tremec so if your ok with the cruise rpoms the 331-342 gives you with your setup then i say go for the gearswap and be done with it.

But if i were you i would also have new ujoints installed and the d-shaft ballanced at the same time.

Just about every time i have been involved in gear swaps that spin the d-shaft faster you end up with driveline vibes due to worn ujounts and shaft out of ballance so i have the d-shaft work done right a same time as gear swap is going on .

that way you dont end up having car back together just to find out you have vibes issues and have to make anohter appt for that work slowing things down even more and most every time i have that d-shaft work/ballance work done i find the parts were worn and shaft was considerably outof ballance and would have vibrated according to the d-shaft shop if i didnt have the word dome with d-shaft spiining fatser with new gear.

I also replace tran's yoke too at the same time if it looks worn at all and even with this additonal $ 175-200 expence to basically rld the d-shaft the overall cost will still be well over 2x cheaper then going with a tremec.

It all comes down to if your ok with cruise rpms the swap to 331 or 342 gear gives you ,thats what you have to ask yourself.

scott

Do you know the new M22Z (2.98:1) gearset will install in your existing Muncie 4 speed.