Re: '85 1/2 Ton Squarebody 400 SBC build?
Oddly enough I did a 406 build and swap on my Dad's 85 K10 about 20 years ago when the 305 gave up the ghost around 100k. He ordered the truck brand new and is annoyed to this day he could only get a 305. His is black and red. Anyway...
It was a rather simple build. .030 over w/ rebuilder pistons in it. I had a set of "good" GM iron heads on hand that I put on it. 2.02/1.60s w/ a mild port job and good valve job. Steam holes drilled. I can't remember what # heads they are but I am betting they were a set of iron bowtie heads as I had several sets at the time. Today I would use a set of Vortecs in a second. Way cheaper and better.
Used a new comp cams hyd flat tappet RV cam that I had removed from another project. Stock crank and rods that were checked by machine shop. Edelbrock performer intake w/ reworked stock Quadrajet. New GM HEI distributor. Exhaust manifolds w/ no AIR tubes and true dual exhaust.
3.73 rears stock and the stock 700R4. Big GM radiator.
HUGE difference in performance. No noticeable change in MPG. Frankly it ran how we both wish it did from new. Isn't a screamer but a lot more torque. We went up the hill towards Pocono Summit right after it was done to pick up a truck load of Chevelle parts. That thing never needed to downshift it just kept right on pulling. In 20 years he has pulled trailers and plowed snow w/ it. We have since had to put a trans and rear in it but that operator related I would say. Gov'Loks do go boom and make a mess inside.