if your talking about the early us or aussie 250 the intake is cast on so you cant do anything easily to them. offenhauser used to make a couple different intake set ups for them but both require a fair bit of machine work. the aussie 250 2v head has a removable intake add you cant buy anything new for them these days. the aussie 250 crossflow head has 2 barrel and 4 barrel manifolds available for them. feel free to contact me if you have more questions. cheers
of course you can adapt a x flo head on to any of that series of 6 cyl engine but why bother.? just use an alloy head aussie 4.1 L (250ci) engine. with 200ci length rods and short deck pistons they love to rev aswell.
but the ammount of work involved would be offset by the shipping cost!
as opposed to the amount of work adapting a US trans to an aussie block? remember that you will need either an aussie bell housing, or an adaptor plate. as for adapting the crossflow head on the US block, check this link out;
you will find the procedure much easier than you realize. the problem jack had was with distributor clearance, but only because he was using a US 200 block rather than a 250 block which would have given him and extra 1.5"
as for the amount of work offsetting the shipping costs, i rather doubt it. remember that there is a large difference in cost between shipping a 500lb engine as opposed to shipping a 100lb cylinder head.