1964 C30 HO72 Axle Swap to 14 Bolt

Hi,

Background: I am working on a 1964 C30 complete restoration and want to swap out the HO72 5.13 133 inch wheelbase DRW axle assembly to a 14 bolt DRW. I have an upgraded custom-built SM420 which addressed the front leaky seal problem and added Syncro for 1st to 2nd gear. Replacing the 230 I6 and old SM420(Original Mileage 65K) with a custom-built Gen 1 SBC. I want the option of doing light to medium towing in the 5-8k lb range with good highway speed. Online speed calculator with 3.73 gears results at 2500 rpm, 30.5 in tires and 1:0 final gear ratio on the SM420 looks reasonable for highway cruising/towing.

Question: What year and options should I look for in a 14 bolt chevy w/10.5" ring gear? Also, I am adding power brakes and discs upfront but keeping the rear on drums. I'm ok with a junkyard find, but will still have it cleaned and gone through (rebuilt), or buy a remanufactured complete assembly. In addition to that, what's your thoughts on optionally moving to 3.55 or 3.4X since I've upgraded the powerplant. Any details and advice on this conversion would be much appreciated. Thanks