Alright, I asked this question 3 years ago but can't find my post for some reason...anyways, I have a 305 TPI out of an '86 T/A that I was going to replace the 305 TPI in my '91 T/A with. Only thing I'm reusing from the '86 is the longblock (block, internals, heads, valve covers). Was going to reuse everything else from the '91.

I recall someone saying something about possibly having to notch the alternator bracket to fit the serpentine setup, and this is really the only thing that I can remember being a potential problem. Anything else I might run into? Any problems bolting the intake onto perimeter bolt heads?

 

The center two intake manifold mount bolts on each side are at a different angle between the '86 and the '91.

 

Alright, so do I absolutely need those center bolts, or can I get by using all the other bolts and filling the center holes with something to avoid a vacuum leak? Has anyone trying drilling and tapping new holes in this case?

 

You need the bolts. All you have to do is elongate the bolt holes in the intake manifold so the bolts will line up to the holes in the head. Some put angled washers under the bolt heads to spread out the load on the intake.

 

yes you need them.
the pre 86 intakes are 90 degrees for the center bolts. your new intakes manifolds are 72 degrees. you can find a shop to fill and tap, or you can get post 86 heads - not the gm vortec ones for the lt or ls engines.