I bought mine from moparts race parts for sale. They may be an old design, but I would say they work pretty well. I built my 340 mainly out of parts I saw forsale, the only new parts being flat top pistons, rods and lifters. The heads were untouched, so I home ported them trying not to make the port any bigger because of the small engine size. The cam is a solid roller with over 260 degrees on the intake side at .050", and the headers are with 1 7/8 primaries, intake Victor W2 with 2" open spacer (just for street credibility) and a 750 holley. It made 587 hp at 7000 at dyno, and has so far run 10.2 in my light '64 Valiant, but still learning how to use the DN 4+1 manual. In this video the engine was sputtering though in all runs since the distributor cap was loose... https://www.youtube.com/watch?v=4Ufoy89RoEQ