First off welcome to the forum, I think your best bet is to find another Abody that has a good v8 drivetrain and maybe not so good body because you need motor, transmission and rear axle and just about everything else radiator, driveshaft and the list would go on and on. If you had the k-frame you would not need to by the conversion motor mounts etc. Wtith the remaining money you could build or rebuild things as needed.🙂

 

I imagine swapping out a 6 for a v8 isn't as easy as they make it look in some of the motortrend shows.
I seem to remember a really good demonstration of it on Mighty Car Mods when they built a "mad max" inspired car. Multiple unforseen problems and hundreds of man-hours that involved every kind of torch cutting and welding.
If you aren't sure where to source an affordable v8 in the first place, it might be more trouble than it's worth...

That being said,
More power to you for setting big goals.
There are a ton of Ram trucks sitting in junk yards with a Gen III hemi just waiting to get unstuck (if I remember correctly, holly makes a rig that learns timing and fuel management as you drive). If you can find a way to match one to a set of mounts and a transmission, you might be able to pull it off.
But, I don't know of any way to do a v8 swap that wouldn't cost less than 6 grand. For that money, it might be better to work with what you got through a reputable performance shop...