The CNC pro head is not bad for a out of the box head, The standard HTCC head is by far way too much trouble to bother with, from ping to high engine temps, to really not making any great power I would take a pass on those. The HD performance heads are not bad either, with some very mild clean up work they are a great bang for the buck if you can locate them cheap. Swap out the seals, CC the heads, do some clean up in the ports and you have a good running head. Out of the box we find the seals to leak, be missing, valve seal to seat poor, and the cc in the chamber to be off a few cc from front to rear. All easy things to fix. But once you have bought the heads, then ensure that you will have many trouble free miles and get the most from them what you you spent?? A ported CNC head with a 1.9/ 1.625 that we do is 850, will flow 149/151 @ 10 inches. They are cut on a 6 axis CNC machine. These are the heads that we make on a 100-104 hp and and 108-114 tq on 98 inch kits with a 37 g and 9.8.1 compression. So looking to haveing your own head ported is always a great idea as you can tailor that porting to your set up vs a out of the box one size fits all.