Father-Son 1974 Duster Project

It's either 5/16-24 or 7/16-20 for the converter.
Special bolt I think because of the shallow head.

http://www.autozone.com/nuts-bolts-...orque-converter-bolt-for-chrysler/193899_0_0/

Summit
http://www.summitracing.com/parts/arp-240-7302/overview/

http://www.summitracing.com/parts/arp-240-7301/overview/