which year 3.8 had the best flowing headers? and would they fit on other year engines? particularly on a Vin C?

Headers aren't available for the 87- Series 1.

The tubular manifolds used from 92-95 probably flow the best, and are the lightest. They MAY swap.

Arent both engines the same block? Also, would the upper intake off a 92 bolt up without modification? What about ignition systems? What are the newer, better engine parts that can be swapped to a LN3? Maybe factory upgrades are a possibility...

You'll want to do the 93/94 L27 heads, they have Roller rockers instead of fulcrum rockers, even though no advertised power gain was ever put out, it'* there. Lower intake manifold, and either the 92 metal intake manifold, or the 93/4 plastic one, depending on the EGR system you have. Getting matching TBs too.

Would it be a good idea to go out and find a complete engine from a 93/94? Maybe ! can find one at the wreckers...

All of the electronics should be similar (maybe o2 etc). If nothing else, you can do www.gmtuners.com.

I'd say easiest way to avoid electronics, would be harness and PCM, but at that point get an L67. An */C setup will cost about the same as a N/A setup too, so think about that as well.

I aminterested in direct swapping fo parts without ECM changes, but an L67 would be crazy... So the manifolds will fit for sure? Why wouldn't the computer accept the different parts? are there sensors and things to worry about? Has anyone ever swapped heads and intakes before?