i started to read some, but couldnt make it through all the posts.
my car is probably around 3500 but i dont think a few hundred lbs will make a huge difference. i am running 3.73s and a t56 with .5 od. as long as i keep it above 1,000 rpm its fine. it will hold speed up hills and still be able to accelerate. 65 mph is around 1500, 80 1900 rpm. it really likes 65 mph. plenty of people said rpm that low wouldnt work. right now im running a holley 3310 and i think the secondaries open somewhere between 75-80 and mpg is cut in half. i just figured that out when i took it to work the other night. i kept a small cam thinking i wanted to keep some good torque down low, and its not a strip car. i built it for road trips. took it to the power tour kickoff this year and i got 19 mpg every tank on the highway just 2 weeks after i did the bb and t56 swap, with wife and kid packed up and the trunk packed full of junk. 3,000 mile round trip.
the mill is a smogger 400 with fresh rings, bearings, the small summit cam, older rebuit 906 heads shim head gaskets, 383 steel crank balanced for the 400 headers and a performer intake. its pretty much just a stock engine. this was a temporary mill as i wasnt sure how it was going to behave with the .5 od. i didnt want to spend a lot of cash and still have to make changes. i think higher compression would only help along with more cubes. eventually id like to build a 451 for it. ill probably stick with a small cam, i like how tame it sounds.