T540
Van requires a straight valve 540, I couln't find the "T" version in my info, but if it has a horizontal FI, it may not be possible to use in the RV10 due to the nose gear/motormount. Straight valve 540s are fitted, based on application, with either vertical or horizontal FI. If the engine is available at a fair price, the sumps are intenchangeable. A,B, C, D,E, F,G series are your best bets, with vertical carb/FI. Bendix or Slick OK and interchangeable. Any of those can be had with horizontal FI, though not very common.
tacchi88
RV10
O540B2B5 now IO 540B4B5