For $70, that's worth giving it a shot. I was more impressed with an HEI conversion on a 258 than a TFI conversion on a 360 that I had experience with. Doesn't mean that's a universal experience, but I would lean HEI if I were to do another conversion in the future. I have no experience with the MSDs, so can't comment there.
'78 J10: 258, 4 speed(T18), longbed, topper
'08 Dodge Grand Caravan
Some dogs, a few fountain pens...and too many sewing machines...