Rear gear swap?

[69restomod]

Hey guys I'm brand new to the forum been a fan of the website for awhile and finally joined! Anyway I am wanting to swap gears in my truck from 3.42s to a 3.90 or higher ,I am looking for the best performance and track times I shift at 6500 and will spraying a 150 shot ,I am running a 30 inch tire and was looking for some advice, any help would be greatly appreciated, here's my setup

69 shortbread weighs 3780 with me in it
11-1 383 4 bolt main
Scat forged crank rods and pistons
Comp cams hyd roller cam 242/248 .584/.579 on a 113 lsa
(Bare with me) pro comp 190 cc heads all new Pbm valves and springs
Ported super victor single plane
Holley hp 750
Quick fuel billet 175 fuel pump with -8 an braided fuel line
Sumped fuel cell mounted between the frame rails in rear
Msd pro billet distributor and digital box
Fully built 700r4 hardened output shaft etc.
Edge 3600 lockup converter
12 bolt posi with 3.42s
Ece 4/6 drop
Ece tubular rear trailing arms