Best carb for off-road is a quadrajet. You'll need a 4 bbl intake manifold and an adapter for the spread-bore pattern of the q-jet, as the 4 bbl intakes for the 225 are all square-bore. I would reccomend the Offenhaeuser Dual Port intake manifold # 6035, cost $200-225. If you can swing it the Edelbrock Q-Jet # 1904 would be a good selection, cost $435-450. Square-bore to spread-bore adapter should run around $20. If you want to go with a new carb and don't want to pay the price for the Q-jet, then the Carter AFB # 9504, (appx. $230), Edelbrock Performer # 1404 & elec choke kit # 1478, (appx. $250 for both), or Holley # 8007, (appx. $260), in that order. It is worth saving for the extra money to get the Q-jet. It's the next best thing to fuel injection.
Tim
'66 Jeepster Commando w/Buick 252/4.1L V-6
'70 Wagoneer w/Buick 350 V-8
'76 Wagoneer w/AMC 401 V-8 (sold)