Need more rearend help and advice...please

[lts70]

Well My newest project keeps getting bigger and bigger. I started out buying some rims for Christmas. I decided to get 5 lug because that was the only way to get this type of wheel. Then I bought 5 lug hardened rear axles from summit racing to swap out my 6 lugs (70 Chevy W/ 6 lug disc brake kit, I already have 5lug front rotors also). Then I decided while I am in there I may as well change out my seals and bearings and put some synthetic oil and posi additive. http://67-72chevytrucks.com/vboard/s...d.php?t=318405

Then I asked around to see what gear ratio I had. My truck is a 1970 Chevy C-10 SWB that from the factory had a 307 engine, a 4 speed with granny low and a posi rear-end. So I was told because of these options it had a 3.07 posi rear-end. Not exactly the best ratio to go with my NV3500 apparently. I think the ratios for the nv3500 are 1st-4.02 / 2nd- 2.32 / 3rd- 1.40 / 4th- 1.00 / and 5th- 0.73 (correct me if I am wrong). So now I have decided that while I am in there I might as well put new gears in it. Hoping that the lower gear ratio will wake it up in lower gears and make my OD more usable.

It does good but the last truck I had this built 327 motor in ran like a whipped dog, Before it was in a 1968 SWB GMC heavy half ton from the factory with the 6 lug in front and 8 lug in back. I don’t know what ratio the 68 would have had. Now it just does alright in my 70 Chevy in comparison what it did in the 68.

The tires I am running at the moment are / Backs 285 70 R15 - Fronts 255 70 R15. If I do go to a different tranny in the future it will be the 4l80E with a 6.0l in front of it.
Please let me know what you guys would do.

Should I just go through the entire rear-end or would that be a waste in comparison to buying a used axle with the correct stuff in it.

What rear-end ratio would you use with my set up and that would go with my possible future upgrade?

Thanks a ton in advance guys