I am no expert and maybe there is a reason for this (the experts can chime in), but considering it's a conversion and things were changed one thing that often comes to mind and trips a LOT of people up are grounds. Especially since it works OK for a few minutes and then trips. Usually a gross error will show up immediately.
It's showing as a TCM issue. Could be coincidental or something could have gotten bumped, pulled, disconnected during the swap.
Missed, forgotten, or poor grounds has tripped up a lot of people over the years and it's an easy thing to forget/miss. Adding a couple extras may not be a bad idea either (can't think of where it would hurt). Until someone with more knowledge (or one who's actually done the swap and can suggest better), I would start with grounds and rechecking connections (for proper connections and/or loose pins) especially the at the transmission and TCM.