Intake and Exhaust plugs????

The easiest way is to use painted aluminum foil and thread.

I was a crew chief on F-15s for 15 yrs we never used the exhaust plugs but for intakes we used a canvas like material or very heavy vinyl fabric shaped like the intake with a lip or pocket the sliped over the top edge of the intake with two bungee cords on each side of the bottom edge that we hooked on the launcher claws for the AIM 7s oh and the fabric color always matched the squadrons color ie... red sections were red covers ext... I'll post a picture in ABMS

Not that this really helps, but...

As I recall (and I could be wrong), the very first issue of the Monogram 1/72 F-15A back in 1974 included the red plastic intake covers used on early F-15s.

Martin IPMS 44668