It's not "like/kinda" a 4-link...there are only Two bars. In a 4-link system, the axle stays nearly at the same angle through the suspension travel. The old truck arm set-up is more like very long ladderbars... in which the axle rotates in an arch around the front pivot point.
On to your question. The height & width of the frame is the same as the newer trucks in the area where the crossmember goes that mounts the link arms, so that will go in with just some drilling of holes. The older frames narrow behind the axle centerline which will create a little bit of work. The upper shock mounts will need to be made/transferred since they are in a different location. The panhard bar (or bracket) will be too short because of the narrowed frame, however it is really too short from the get go. It should be as long as possible (like on the Third gen Camaro & Firebirds for example) so if I was bothering to do the swap...I'd make a new, MUCH longer one anyway.
A swaybar is a near must on that style of set-up if your planing to do street driving...they will "roll-over" big time in a bend!
your right it will "hook" up way better then leaf springs will.
Sorry, I don't agree with that. I've seen a couple trucks run well with that set-up, however there is nothing wrong with leaves & some Cal-tracs or Max-tracks, ect. Guys are going quicker than 1.20 60 foots on leaves & Cal-tracs on tires WAY smaller then you can put under our trucks.
My Two Cents...Stick with what you got. Do a flip on the axle, buy/build some traction device (Cal-trac) & some decent shocks & some real tires...you should be all set.
The wife's been 1.55 60 foot with just some stuff I made on 325 Et Street Radials. It can be done rather easy. Lorne