727 or 904?

904 all the way. Screw that 727 boat anchor.

Have the 904 built. Can easily be built to handle your hp. No need for a manual valve body either.

As far as od goes. gear vendors is probably the easiest way to do it. Not all that cheap and not the best od ratio but a very strong piece that you don’t have to hack your car to put in.

That a500, 518 and gm200r od units all require you to hack the torsion bar crossmember up. If that’s not a big deal to ya then that me be the way to go for you