Others will disagree.
I think you'd have to be totally bat-shiit crazy to expend that much time, money, effort, and enthusiasm on a piece-of-crap 8.5" 10-bolt axle. You'll sink a thousand dollars worth of effort and materials into an axle that is under-engineered for full-size trucks, should never have been used to begin with. It will have no reserve strength if you upgrade the engine later. And you still haven't dealt with the ****** rear brakes that 95% of these axles are used with.
START with at least a 9.5" semi-float "14 bolt" axle, have custom axle shafts made to suit whatever width you end up with. That axle should have 11.x Duo-Servo rear brakes which is a MAJOR improvement over the 254mm (10") leading-trailing shoe drums.
If you INSIST on going through with using/modifying a "Ten-Bolt"--and obviously I DO NOT recommend it except as a "practice run" on a discardable axle to detemine the exact scope of work, and to decide if you have "enough" welder and welding skill to attach steel axle tubes to a cast-iron center section and end up with an axle that still has the bearings in-line with each other--look into late 1970s Cadillac Seville axle shafts, and in fact the entire axle. I have no figures, and I'm way too lazy to look it up. The axle is another 8.5" ring gear, suitably used in a "compact" car having an emissions-choked (Olds) small-block, using the 5" bolt circle and rear disc brakes. Seems to me the first year of production ('75) had rear drums and 4 3/4 bolt circle, but was improved for '76--'79. Maybe you just cut off the leaf-spring mounts and add whatever mounts suit your purposes.
Also, for whatever it's worth:
Instead of a "4-link triangular suspension", consider GM's Gift to NASCAR, the 1960 style "Truck Arm" rear suspension--Two triangulated arms and a Panhard rod. Should be easier and cheaper to make, and it was good enough for 150 mph.