The difference is the repro is incorrect in the ribbing in the front and has two drain holes in the front as well that 69/70 did not have. See my ECI thread for an original HT full pan transplant into my 'vert (both '69).I believe the full replacement floor pan works, it just isn't 100% correct. With any re-pop metal, you do have to do a lot of trimming and cutting.... but I think the issue is the structural stamps in them don't match the original, so if you are underneath you will know that it has been replaced. (This is just what I think remember reading before, I would have to double check though) Taking out a floor is actually less work than most would think, there are a bunch of spot welds that you have to drill out and they actually make a tool for it. Once you have those out it just takes a little prying and muscle to get it out.