Cruise friendly low 12's with a 340 Dart
I have the adjustable pinion snubber which works well when it hooks.
Gear vendors OD looks interesting but at nearly $3,000, it's out of my budget. For a casual cruiser, you'd never recoupe the expense. The 518 swap makes the most sense and is the cheapest route IMO but I just hate the idea of cutting my floorpan to make it fit.
Other people have mentioned a TBI setup or even swapping carbs for long cruises. I even thought of just disconnecting the secondaries for cruising and running the primaries pretty lean.
A couple of people have also mentioned dropping down to a 4.5 powervalve since I pull 10" of vacuum.
Keep the ideas coming!!