engine differences

are there any differences in the 90-94 4g63 and the 95-99 4g63??? besides the slight difference in power???? also i read on a forum on here a long time ago that there is a way to put a 4g63 head on the 99-05 2.4cyl???? is that a huge gain or not???

the 90-92 or 93 i think, is the 6 bolt motor and anything newer than that is the 7 bolt.

Edit:Do some searching to find out anything more than that