I've got a f100 ranger 4x4 short wheel base. Stepside. It's got a 351 modified to a 400 and a stroker kit putting it at 406 stroker. It's got 3.10 spool Adrian racing gears a c6 transmission. And my issue is that it keeps breaking the flexplate. We've replaced it twice but it's broken twice with stock rated flexplates for this motor/trans setup does anyone have input on what to do. Preferably with links I can't seem to find anything that isn't 500$ flexplates

 

There are stronger flex plates you can get. The trash you get at the box store is as thin as it can possibly be while still meeting the factory spec numbers. When I was rebuilding my C6, the local transmission supply store owner told me this is a common problem with the box store parts and if I was breaking flexplates to come back to him. I was only running a stock 351 HO and didn't have a problem.

If you have a major city near you, look up a transmission parts supply store there. They'll have all the parts options and can order what you need.

PS: $500 is exaggerating as I found a website with "racing flexplates" for ~$300.
http://www.atiracing.com/products/fl.../flexplate.htm