I am thing about this .. often lately...someone may want to try it.
Take a 750 A head with a smaller port, Then on the top edge of the intake port spigot, build up with weld or JB. Then port as normal, but move intake hole Upwards, just under the original top of port. Should raise it 2 or mm. Just thinking that the A head having more meat, may give more room to work with.
Maybe it is just easier (on any head) to bore out the spigots, remill the hole, then weld in turned inserts.... may be quicker to port that way.