arent the heads diffrent from a old school carb to the tbi? im pretty sure there both baisicly the same block but i always though they were at a little diffrent angle compared to each other. what is all the diffrences between the two anyway beside the fact of carb and tbi?
TBI blocks had a one piece rear main, some were roller ready, some can use a fuel pump some cant, crank is completely different on the back (better design, less leaks) heads had center bolt covers for better sealing, the middle two bolts on the heads are at a different angle, but nothing a die grinder cant deal with.
Carb blocks (excluding 1986), had 2 piece rear main (Known to leak), none were roller ready, heads had perimeter bolt valve covers which are known to leak.
One Peice rear main
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Two Peice rear main
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both together
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If you are set on using a 4-bolt main (which is really a joke, 2-bolt is just fine), TBI blocks did come with 4-bolt mains, my current block is a 1989 638 Casting, 4-bolt main, Fully ready for roller and fuel pump. 4-bolts are more common in heavy duty trucks, mine is out of a 1989 V20 Suburban (73-87 style, not 88-98 style)