First question really is; do you have any knowledge of this stuff? or will you have other people do it? and then how much do have to spend on this? Do you have a budget or not? I don't know about the bigger frames, and I'm not sure how many people here know if the change will work or not, but on the smaller trucks there needs to be some changes. But since it is an older truck, the frame is smaller, so just sit tight and have a few, and I'm sure somebody who knows more about these trucks will help you out. A V8!!! Get lost

No 292 or 302 Jimmy? No really, it all sounds good to me, but what do I know, not that much (only been into this stuff since I was 12, and I'm only 17 now).
Good luck on your project, and build it for yourself, the way you want to, that's the most important thing.
Nate