Doober said:'92 doesn't have Vortec heads, those started in '96. Only major difference if you keep the '92 TBI heads is the inner two bolts on each head aren't at a 90º to the intake mating surface. You could buy an intake with the holes drilled at the correct angle, some guys just lengthen the holes on their current intake. The TBI heads are good for torque down low, but are pretty much done by 4,000RPM in stock form.
Far as 305 350, any year will work, but there are certain things to consider. '87+ 1-piece rear main seal blocks use a different flywheel (which has a bolt pattern different from a pre-'87), but besides that everything bolts up just fine.
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