Truck manifolds on Dart Sport?

Ah, my car is a 75. I suppose that means I can't use this particular trick?
That is correct. The spool mounts can't be shimmed up without a lot of cobbling to make it happen. If you use Dougs D453's and a mini starter as @TrailBeast suggested, you won't have any problems. I have gone to Autozone and bought 4 or 5 mini starters for a 92 Dodge B200 van with a 5.2 engine. About the 3rd one, they counter guy asked me, "How many damn Dodge vans do you have?!?" LOL. I use them on everything. They spin fast and don't sound like a cat with its tail hung in a washing machine ringer!

To also answer your original question, forget the truck manifolds and find some 72 and up 340/360 A body exhaust manifolds. They have to be from an A body (at least the drivers side) or they won't fit. 68-70 340 HP manifolds work great but cost more than Dougs D453's nowadays.