I was very happy with my Aqualu tub for my '74. Very sturdy, well-made stuff. The "instructions" were a little light, but in true man-style, I didn't pay much attention once I figured out that it was fairly straight forward.
I bed-liner'd the inside, spray painted the outside. Had to use a special primer made for aluminum but no big deal. It's not 'original' but I didn't want to replace everything with steel - no time, no talent for it! And no more rust! The tub went on, bolted down very quickly.
As with all major assemblies like that, be sure you don't tighten ANY bolt down until you've got all the pieces together including front fenders, grill... I mean all. Yep, that's the voice of experience!