Big "depends" here on the temp. A bb Mopar has siamese exh ports so it needs good cooling in that area, especially with nitrous.
You have a Megablock, shouldnt move around too much hot to cold, IF the carb works well, you should stage at 100* . That would require towing up . Like i said, the carb must be tuned for this temp so dont go try it and say it didnt work...LOL
Like i said this is for a decent amount of nitrous use on a BB mopar....i dont want to argue it, just saying what i have been instructed to do by a very reputable builder and what has worked for me. I have a Dale Cubic carb and it goes on the brake no problem, usually stage at 90 to 110*