Advice Needed on Diff Re-Gear/Tranny Swap Dilemma

[bcoke]

Hi! I'm new to the forum and have only had my blazer for 6 months, so you'll have to pardon the ignorance. I'm looking for some advice on a problem I'm having: how to get my 72 Blazer on the highway.

It seems like the last owner wanted it to be a rock crawler, but I'm looking for it to be more of a daily driver. Right now she screams at 55. My goal is to be able to eventually take her on a road trip and cruise the highway at 70.

Here are the current specs:
TPI 5.7L 350 engine
4 wheel drive
Turbo 350 automatic trans
NP205 Transfer case
4.83 gear ratios
1 ton axles
35in tires

I don't need the towing capacity of the 4.83s (at least not right now), but if possible I'd love to keep the torque while increasing the max speed. I know that that might be asking for too much, though, and just might not be practical.

I prefer a manual trans, so I'd like to eventually swap out the automatic for a manual, but I can hold off on that if there'd be a better way to get the truck up to highway cruising speeds right now.

It looks like re-gearing the diffs (have to do front and back since its 4WD) will be around a $2,000 job. That's creeping toward some tranny swap prices I've seen, and it seems like it'd be a shame to knock down a beast like this to something like a 3.55.

So my questions are...
1. Would a swap to a manual tranny like an NV3500 give me what I'm looking for in terms of top speed while keeping that low-end torque? Or would I have to regear the diffs even with the tranny swap?
2. Would adding an extra gear to the current trans setup give me the required speed at a price that's more reasonable than a tranny swap or a diff regear?

Any advice or ideas would be greatly appreciated. I'm open to everything. Thanks in advance for the help!