Thanks! That's 64mm at the narrowest. So the 4.5 throttle body must be good for the 5.0 then. The Djet throttle body seems also easier to match with a TPS as there's already a Djet sensor attached there. The Kjet Throttle body requires more work due to its shorter shaft.

I visited Barry's website already. That's what encouraged me to go the same way. He told me he uses the blue injectors on the 4.5 and that their flowrate is too big for proper idle tuning. I will be using the yellow ones that I have on the 3.5, as they have a lower flowrate:

The Bosh reference for the 4.5 blue injectors is 0 280 150 036 and their flowrate is 485 cc/min at 3 atm.

The reference of the 3.5 yellow injectors is 0 280 150 034 and their flowrate is 338 cc/min at 3 atm.

According to this web page : http://www.megamanual.com/v22manual/minj.htm#size I need injectors with a flowrate of 212 cc/min at 3 atm. On that same web page there is a calculator to get the flowrate at different pressures. With 2 atm, the blue injector still has a flowrate of 403 cc/min while the yellow one has a flowrate of 280 cc/min. It's a bit more than what I need, but I think it will be workable.

The Mustang injectors have the advantage of being high impedence and do not require the flyback board needed for the low impedence injectors. But they require some machining to fit the Djet rails and I'm not sure I can keep them in place on the head with the same system. All in all, fitting a flyback board seems to be less work. I wonder if Barry fitted one though.

As per the 4.5 manifold, I'm left to determine if the inner section of the ports is the same as the one on the 5.0 engine.