Re: 5.4 lightning engine
I don't know of an adapter plate for the SOHC modular motor to G50, but it should be the same as the DOHC 5.4L motor (found in Lincoln Navigators, Ford GT) since the block bolt pattern is the same - as far as I know.
However, I've got a Lightning and I don't think there is any way that motor is going into a GT40. It is extremely tall with the Eaton supercharger and the way they did the liquid/air intercooler that sits on top of the motor. I suppose if you didn't mind the blower and throttle body sticking up over the top of the car it could be done, but otherwise I don't think it'd fit. You can get some height relief by using a Ford Racing Whipple blower on the motor, or a Kenne Bell screw blower, but the height difference isn't much.
You'd really need to convert it to a dry sump to get some height reduction as well as use an alternative blower. Even then I think you'd have a tough road to hoe. There are some pictures on the site showing a 5.4L DOHC Ford V8 in a GT40, looks really tight. Add another 10" on top for the blower and it becomes a real problem.
If for a GT40 do yourself a favor and build a good Windsor.