i have a stock 1987 chevy 305 that i bought for a truck i got will an intake off a 1974 work? if you look it up at summit or jegs they go up to 1986 and a different part # for 1987 and up. is it just an emissions thing or is there a differece in the heads?
Look at the difference in the angle of the two center bolts on the intake. They are at a different angle on the 1987 and up than the older ones. Some folks SAY you can grind the old intake openings to match ... but I never have. I just got the correct intake. They have been out long enough now that they are cheap to buy. Back in the late 80's and early 90's ... they were considerably higher than the older style.
Edelbrock (at one time, anyway) sells or sold special wedges that allow the use of a pre-'87 intake on the later heads if you drill the four center bolt holes oversize.
I'll go out on a limb here. I think the older style was retained on truck engines for a year or so after the passenger cars were changed. I know that the "Mr Goodwrench" of that era had the old sytle heads on it. I was suprized when I picked up a used one that had the one piece rear seal, but still had the flat tappet cam and the old style heads on it, even though the block was cast and machined for the brackets to hold the roller lifters. But if the intake bolts are at the same angle, it's the old style.
if it has center bolt valve covers - the center hole are at a different angle than the early 4 out side covers --- center bolt vortec use only 4 intake bolts per side .... know people that reamed center holes on old manifolds with no problem