P90a cam will die in the 79 head.
The difference for your goals is really not much of a bother, stick with the 79.
100k on this engine, esp. if cared for, is nothing!
One problem you may face in the N/a setup being used for turbo application is the metal inserts in the 79 head. This is a debatable point, however, they help in the transition of gases leaving the combustion chamber so you will want to keep them.
Ping will be a little more of an issue with the one point increase in comp ratio.
Nothing that a little meth injection can't handle.
If your engine is in good shape, 100k or so, don't mess with it, turbo it slowly.
Put your money into gauges, wide band, edis or MSD, meth injec and most of all
READING! (I know you are, just wanted to throw that out there.)
Do a more creative (expensive) engine overhaul when you are more comfortable in the saddle.
This is only my opinion, good luck.