Rear End Posi Help!

[leftybass209]

So, i just decoded my rear axle and it's an HB which if I am correct, is a 3:07 rear end, and I cracked it open to confirm it's posi. Unfortunately, the truck has a 700r4 which is no bueno with the rear end gears for overdrive. My question is, can I swap out the rear gears without swapping the posi unit? I see 3:73 gears through companies for anywhere between 150-200 which isn't bad at all, I just don't want to have to dump another 500+ on a posi unit. Any help is greatly appreciated, thanks!