Have a look through your t series engines... are any of the heads twin cam??? That's the 2T-G heads you can nicely bolt onto the 3T (larger capacity) blocks... slap some side draught webers on that and a blow through/draw through supercharger running about 7 pound of boost (more than that and you'll be wanting to fill the block with forged gear first...)
even a turbo charger... a 3TGTEU turbo manifold can be sourced relatively easily from the US.
The twin charge setup might be relatively easy to set up also, considering and there's the emmissions control system on the 3T-C (which i guess will get ripped off.) that has a nice bracket that looks like it might do good for mounting a SC-14...
Or, send all your T-18 stuff over to me... I'm building two atm... actually, i'm in an almost identical situation as you are now, except my rusty T-18 is licenced...
It depends on what you want at the end of it all... You could work with what you've got, and end up with a good car that still might not suit your taste or style, or you could, as you said, fix up one and sell it off to fund another... In my situation, i love the shape of the T-18's, so i'm going to end up with two cars I love.
Really comes down to your personal tastes though, so work out what you'd like first...