i may be wrong but the pgm 4 is heavily restricted thats why a pgm 3 was used. i dont think you will have any where near **** 72 bhp more like 40 bhp, mc 28s are known to be heavily restricted and hard/ expenive to de-restrict.
im not a expert on mc 28 de-restricting but i think you will be dissapionted the mc 21 flywheel is a great idea but i think the pgm 4 restricts powervavle opening and retards the ignition in 4th,5th and 6th