I have a small dilema

[swtman]

I have a '67 gmc with a 305 4bbl mated to a turbo 350 and 3.73 rearend. I love the get-up-and-go with the gearing but can't drive highway speed. Here is my dilema, I would like to change the tranny to a 200-4r but not sure about moving the crossmember and especially setting up TV cable and wiring in the lock-up t/c. The other option is to change my rearend gearing to something like 3.08 but I think I have the original driveline which is like about maybe 2" in diameter (pretty small) and 2 piece and I am not sure if it would hold up to the gear change. If I was to go with 3.08 there will be more torque on the driveline then with the 3.73's ,Correct?I would miss the take-off at the lights but really am more concerned with milage and highway cruising. As it is now I can't enjoy going for a cruise on the highway. So I guess what I am asking 1) will the small driveshaft take the gear change-I do have a heavy foot sometimes!! or 2)Is it really a big deal to swap to a 200-4r and get the TV cable setup and t/c wired properly? Thanks in advance for any Info!!