btw, nate, if you want a v8 that'll drop in with no mods a buick 300/340/350 will be it
lots of torque out the box, and can find a running one with 80k for 50 to 150 bucks
uses same mounts..only thing you may have to rework from the previous buick v6 setup would be the exhaust downpipe and maybe a larger radiator
buick 350 is the lightest at 450 lbs...unless you find the 64 300(iron block w/ al heads/intake...400lbs   all iron 300 is more like 468 lbs