If I had the money, hmmm let's see. I would first search the net for a jdm parts importer or clip importers. some decent ones are
http://www.j-garage.com or
http://www.flashoptions.com e-mail them and inquire.
SPD racing should be able to help also. (don't you guys have a europe, uk, australia hook up or some where over there?)
If you got ahold of a from clip I think that would be the easiest. Pull everything out of the a-spec. Cut out the firewall and weld in the rhd one. get it sand blasted and painted. take apart the whole dash and run everything needed through, steering column, wires, pedals, center console, panels, etc. Put the rhd dash in with the cluster and such.
Now I'm not sure if they had msp's overseas but stuff would have to be custom made if you used the stock engine/drivetrain from the a-spec. So if the j-spec motor is the fsze I would just use that motor (if it's the fsde i guess even better), msp manifold, custom downpipe, and you would have to get the piping custom made, no biggy there. Also use the ze tranny so all the linkages/cables hook up. I would probably also use the US ecu since it's "built" for boost. I don't have deep pockets so a standalone won't be an option.
So let's see you would need . . .
a clean ass front clip - hopefully no more than $3000
a good hook up on body work - that stuff isn't cheap
someone willing to swap the stuff - more time and money
and some nice ppl to help.
If anyone can correct me or add info that would be good. I'm no expert but I want to help. Now, this isn't the only way to go but I think it's the best. I mean you could just get bits and pieces like the dash, panels, cluster, steering wheel, accessories, cut the firewall yourself, and get whatever is needed custom made. But see what your options are and parts are available and go at it.
Make sure you have a back up car though. If you don't have one honestly it's the first investment I would make.
I get s*** for wanting to do stuff like this all the time. Ppl everyday tell me not to waste my money and buy something like a evo/sti. I want to get another turbo tercel like I had, that was pimp stuff.
Good luck and keep us updated.