I put a 466 cubic in big block in a 79 hatch I had years ago. I made the oil pan, engine mounts and headers myself. Because the parts that existed at the time were just pick up parts. The engine mounts they sold you were from 80s to 90s model Ford F20/F350 trucks, same with the oil pan. I saw a couple of other cars that had big blocks swapped in back in the 80s, before I started my swap. Everyone of those, the engine set way far forward and fairly high. I did not like what I saw, so I made my own oil pan and then mounts, then I made the headers. I used a stock K member, since that was all that was available back then. It fit very nicely. I built a C6 transmission for it., then had a 9" rear cut and narrowed for the rear axle. It had 31 spline axles, nodular case and a Detroit locker.
As for putting a manual transmission, you could put a big block top loader, that will handle the power with ease. The other options are to use a TKO or TKO 600, if you do that, you will need a spacer for the scatter shield. The scatter shield for the big blocks, is made for a top loader transmission. The TKOs use the same transmission to bellhousing bolt pattern, but the TKOs use a longer input shaft. I think it is either 1/4" or 3/8" longer, I don't remember. I worked on a Cobra kit car years ago that had a 521 cubic inch Ford Motorsports 620 hp crate engine in it, they put a TKO transmission behind the engine with a common Lakewood scatter shield. I made a spacer to go between the scatter shield and transmission, that fixed the input shaft length problem.