You might wanna just try running a tight front diff instead of a spool. A tight front diff can give you alot of the same feel of a spool with a little give for the driveline. Diehards will say "spool, spool!", but if it is going to be your first time putting the car on the track you might wanna consider starting out with just the regular LW steel diffs in it F/R. Just a suggestion.
Im glad your driveline turned out nice and smooth. A little time on the bench goes a LONG way! I finally started using the "white" gears in my FTTC4, i think they are a little quieter than my original gears after break in. I am in the process of a rebuild myself and found that the tranny pinion gear is rubbing the inside of the rear tranny case... just barely. Ill run it again this weekend and see if it gets worse before i do any major adjustments. Let us know how the car does for your first time out with it!!
- DaveW