You must not be in the right circles.
Dodge R5
Mopar R5
Mopar/Dodge R5 swap and Tech
These are all fb pages full of drag racers running these.

Installed a eei chip gannassi cup engine engine in my car 5 years ago. With a truck roller cam went 5.82@118 in 3,000 lb car with a best guess converter.

Been running these R5 ever sense. A few years back designed a bell housing to use with Reid case pg and t400 transmissions. Sell the whole kit. A couple folks made adapter plates for transmissions. We all have had trouble keeping up from time to time. I took the plunge and order 15 from manufacturer and sell a complete kit with flexplate. Also sell complete transmissions.

I have been 5teens with the r5 I run now. If not for some failing parts in rear suspension would have ran in the high 4's based on 60ft and mph.

Quite a few in Europe and Australia drag racing these also. Haven't seen anyone take the R5 out to go back to what they had.