I would still recommend a hi mount.
The distance, that turbo size, and exhaust cooling is just no a solid combo if your hunting quick spool rate.
I regular 76mm magnum with down pipe correction would spool a lot faster. But then your loose your top end power if the bigger turbo.
It's a trade off. Down low from
a dig off idle or up hi.

 

Simple converter swap might help issue..

 

Ya, right now I can foot brake it at the track to 2900-3100 but the rear tire will start to slowly spin at the line. If a small nitrous kit would make it come alive instantly at the track I will do that. Trick let me know, you can pm me what you can do for me as far as options and pricing thanks again

 

If one were to go to the BW 480, what a/r size would be best for a rear mount? Higher or lower?

 

The 87mm turbine may be a better fit for the 480 if you choose to go that route. The 83mm turbine is a lil undersized for the 8 bladed 80mm compressor. Maybe an s478 with the 6 blade compressor, much lighter than the 80mm.