I just went through this with my Toad. Planned ahead and bought the exact wrong thing! I bought one of the Blue Ox Drop/Rise receivers. You need to check that the length of the shaft of the receiver going into your MH will allow you enough clearance for the riser to clear your rear cap.
The original one I bought had a shaft length of 6 1/2" and the riser would not clear. Had to get one with a 10" shaft so it could pin to my MH and the riser would clear my rear cap.
If you use an extension it reduces the weight rating on the receivers.
I would also check out amazon. They had the best prices and if you are a prime member you cant beat the free two day shipping.