JB Weld works wonders...
I've never had a Ford Racing block in here, but the complaints I've heard about the pistons coming too far out of the bottoms of the bores were on those particular blocks. However, I've never seen it in person, so I can't really comment on that combination.
I see no issues with the Dart blocks....same results as with a regular production block. The
oil rings have to have support rails, but there are gazillions of 331's and 347's out there running around without issues.
The Dart blocks are good about already being clearanced on the bottoms of the skirts. I've had up to 4.100" crankshafts in their 351W blocks without having to touch them. Of course I always double check just to make sure.