Hi Tim.. heres my thoughts....
Not sure you will need the forged jobbies at all.. and be careful of considering the cr upping if you intend to run nitrous.
Balancing is fine, but unless you intend to rev more - not really beneficial or cost effective. (and I wouldnt like to rev the std crank much more than it is already) -
Cams, the only ones about I am aware of are the reprofiled jobbies.. no probs with reprofiling, but they arent really producing the goodies..
If you want it for strip times or the odd burst, then the nitrous would be best - for example.. you could easilly get the 6-7 bhp that kent cams make midrange only (they dont produce more top end), by simply uppng the nitrous.
I am looking to run about 100-125 extra with nos on the 172, I will be using a gear pos / rpm linked, delivery controller with traction control and programmable r****d. (Prior to the turbo conversion)
Ths is SIMPLE to set up, there are guys running nitrous with nowhere near the output they quote, all that needs to be done is set it up on the rollers for the power you require.
You could use the turbo crank, this is humongous and far stronger than the 172 unit.. I have 3 if you want one (new).. these would take as much torque as you could throw at them, the rods are already pretty bloody good, and the pistons do not appear to be a weak point.
Might be worth considering a simple paddle clutch plate too...
Sounds like that little flying machine of yours is gonna be ballistic !