Is the stock type transmission mount strong?

If you do want to go to the later style spool mount, it is an easy bolt in swap. Just need the crossmember and then the spool mount and associated through bolt. Everything else stays the same. If you get a complete crossmember and old mount together, you can buy just the polyurethane inserts and then you don't have to buy a cheap replacment spool mount. I run that way on my Dart.