400's are they any good?

Go to moparts.com and ask 383man about his son's 400 Dart. Pump gas, .557 MP cam, Eddy heads, very mild, very streetable...11.40 as driven on the street with 3.91's. (Well, with slicks...)

I had a 400 back in the day, (early 80's) and a Duster and no money. I decked the block to get the compression up, used a MP templete ported set of 915 heads, a MP .509 cam and TM6 intake. With a 10" converter, 3.91's, a 'glass 6-bbl hood, it finally went 12.30's uncorked on a McCreary dirt track tire. 12.60's corked up...

They need reasonable compression and they will respond accordingly.