I'm "tinking" because I had a Cleveland before my FE. I know the bolt pattern is the same because the gaskets are interchangeable, but the 351C has a stepped recess in the block (as I recall) that keys the thermostat in place. The 460 probably doesn't, but that shouldn't effect your issues since your putting it in the Cleveland.
http://martelbrothers.com/product.ph...9&MMCF_froogle
Not sure; why don't you go to a shop; take the expansion tank and then look at a Cleveland housing and see if you can cut the flange to fit. Or; look at one of the aftermarket Swivel housings and see if you can use one of them. You can tack it fixed so it doesn't swivel and maybe butcher it to fit the tube extension to the tank. Sounds like a fun winter project/challenge. Frankly; if you got enough cash, you can fabricate anything.
Bernie