Thanks Rusty. I have a buddy with a 68 dart, I'll get him to come by and do some checks between his and mine.
Oh wait, that sounds kinky! Didn't mean it that way :)
No offence, but you ask, and several people tell you, but now You still have to check and measure between a 66 and 68 ‘to make sure’. Why bother asking to begin with? Many people here have and share a lot of knowledge but it feels like a waste of time when it doesn’t really get used.
Early a bodies are narrower. Period. You CAN put your magnum in it, it will fit. you need stock 273 exhaust manifolds OR as Rusty and Mopowers Both said you can use headers made by Doug’s, Spitfire, or Laysons if he makes his own, if Laysons doesn’t he will be a dealer for each of the other brands. If you act NOW I actually think there is a set for sale in the classified’s of this forum right NOW. Have a look.
Make sure you use the right motor mounts for the 66 with a v-8 application. You will also need to make sure you have a v-8 Centerline.
I find early A-bodies harder to work on and part finding is also more difficult, so perhaps really do listen the folks who have been working on them for along time now. It will save you time and money