Look at the Ron Francis harness's.
I have used them a couple of times and am very happy with the results. It's the harness that FFR use for their cars. Very easy to install and you can buy engine harness's to suit the main harness. Very well priced and you get a nice install booklet and a wiring diagram you can take to a spraky if you have problems.
FFR-06 Factory Five MK3 Roadster & Type 65 Coupe-Ron Francis Wiring