Let me get this straight, you are just swapping in an aluminum headed LT1 for an iron headed LT1?
IF you are using the Impala SS wiring harness, computer, MAF, etc. it should work fine, as long as:
1) Your old motor was actually an LT1 and not an L99. The L99 is a baby LT1 and would have been programmed differently.
2) A lot of the big cars had 3" MAFs whereas the fbodies had 3.5" MAFs. If you put a 3" MAF on an Fbody (with the ECM expecting a 3.5" MAF), it will get lots of detonation under load. Trust me, I've done it before. I don't know if Impala SS had a 3.5" or a 3", but whatever MAF is on the car, leave it alone. Don't switch sizes unless you tune it.
The longblock on an iron headed LT1 is pretty much the same as the longblock on an aluminum headed LT1. The 97 will have a slightly different camshaft, but not enough to need a new tune IMO. The cam and compression change are the biggest differences. Aluminum headed cars are like 10.4:1 or so. The car WILL run with the fbody engine in it, as long as you retain all the Impy SS wiring, MAF, computer, etc. I would put good gas in it and give it a run, it will probably be fine without a tune.
Keep in mind also that the 97 LT1 will for sure have a vented optispark which will help the opti live longer. That Impala might also have a vented opti, not too sure. 95 was the year the optis changed, so it could be either vented or not. They are not interchangeable, but the wiring for all that stuff will be fine during your swap.
Then when you get it running good, put a 150 shot on it. LT1s love nitrous.
