triangulated vs 4 link, 61 vs 63

[Dustin07]

So I have two questions...

I don't see a lot of 'kits' available for a 60-62 chevy 1/2 ton... they start in 63. Why is that, what is the difference between a 1961 chevy 1/2 ton and a 1963?

My brothers is a '61 stepside (SB) and we are looking to bag it. My '99 silverado is built using an AVS parallel 4 link + panhard bar. I also used a KP Notch with the bends for my '99 frame shape ($250). To save money, I want to notch his using 2x4xappropriate thickness.

So while we're doing his, I'm considering a triangulated since we haven't done one before. What's the biggest difference between a tri-4link and parallel 4-link? so far I like my parallel. I've put probably 4-5,000 miles on it.