with a ca you are reengineering the whole car
its a big job,cutting out floors, swapping diffs, upgrading brakes. rewiring for efi......

a15 is a piece of cake.just a bigger one of what youve got now

if you are mechanically minded and good with electrics you can do most of a ca yourself
do your research before you start and make sure you are capable of finishing it

a finished a15 is better than a ca in bits
dazza