Shopping for a dart and want to swap in a big block...got some questions.

If you're looking for a big block Dart, good luck. The magic years are 67-69 inclusive. Of the factory installed 383s, according to Govier's records, there were 457 built in 67 and 2106 in 68. Not included in these totals were 48 that were factory built for Mr. Norm's that had 440s. Also not included in the count are 80 S/S Hemi cars built by Hurst in 68. Sorry, I have no data for 69. Not known are the numbers of each year that survive in the hands of collectors. The point is that the number of BB cars to find is extremely small. Pricing will be commensurately higher than a non-BB car.

If you find any of these cars with disc brakes, bear in mind they will be the SBP Kelsey-Hayes units, unless they have been converted to BBP floating caliper brake. There's nothing wrong with the KH brake, but the SBP is going to limit the choice of aftermarket wheels and tires.

If I were to put a BB in an A-body, I'd try to find a genuine BB A-body and check out the underside for reinforcements to the K-member and the presence of torque boxes on the chassis. Then I'd duplicate those on my car.

Mopar Performance lists a .890 diameter torsion bar for the BB A-body. Most around here seem to be running .990 and larger. I run a 1" on a small block and think it's fine.