I have a Silvertop 20V engine/trans and complete harness(no fuse box). I was going to do the install in my 89 GTS. I just bought a black 91 GTS with a smallport red top to fix up for the summer. should i get the rest of the parts for the 20V swap or refresh the Smallport. I was told they are close in power + cams, just as powerfull? What should i do?