The 500/518 has a noticeably better OD than the Gearvenders. That was the deciding factor for me. As to the power loss, that is an interesting question. Does anyone know for sure the difference?

What body is it going in? Only a little massaging was required to put the 518 in my Cuda. As to reliability, a properly built 518 can handle what you throw at it. It handles my 540 Hemi as easily as it handles the diesels.

In fact, how about a well built 500? It takes less power to drive. Would require even less ,if any, tunnel mods. And is lighter than even the Gearvenders.

When going behind a big block, the bell housing situation makes the conversion more complicated/expensive. But for small blocks, the 500/518 seems a shoe-in.

https://smrtrans.tripod.com/smrtransmissionsintro/id6.html