I'm never thrilled with using a 2004r in anything but a gn.
There are some guys out there that have dedicated their entire career around that trans and trying to make them last behind big hp with pretty good success.
Multipliable problems you run into. They work OK for just a cruiser. As long as your not too fussy about shift timing, rpm of wot up shifts, speedometer calibrations.
For starters, you need to start with a BR coded gn transmission. Almost every part is improved over a stock 2004r.
If you get serious, call my shop and Ill give you a laundry list of do's and dont's.