Can you and how easy/expensive would it be to either change an EVO 1340 from carbie to EFI? Or fit a 103ci EFI motor and gearbox to an old '94  LowRider frame?

Thomo, can I ask why you want to go to EFI ?
You may gain a bit better fuel economy, but a decent Carby bike is nearly an equal in all other area's.
I'd say budget about $4-5k, Including either custom wiring for a late HD style system, or an aftermarket EFI system like Motec.
Don't forget you also need a high pressure EFI fuel pump/regulator etc'.
Do a search on " Megasquirt" . It's a DIY EFI system.

Thanks for the advice fellas. Just trying to get an idea of whether it would be worth doing up an older bike or just going with a brand new bike?? Decisions, decisions.

There is a company in the US called PFI performance that do a complete kit for carb to EFI.The kit is complete and is $2000.00 dollars us plus shipping.The only problem that i have found is the maps are set up as close to the specs of your bike engine as they can as there are so many different engine combinations and there altitude is different to Australia.So you then have to get some one to create a new map which could take many hours on a Dyno.I looked into it for my bike and decided it wasnt worth the trouble.There is also a article in the latest Heavy Duty magazine in tech torque.