Tamiya 1/48 P-38 conversion

I think that would be a bad idea, use another kit in case the build goes sideways.  Different supercharger intakes, different front and lower cowls, different intercooler shape on the booms, landing light changes, probably a different windscreen.  Dive flaps on the L, but that's an easy change.

Sorry mate.....the Tamiya P-38H is the bee's knees. The Academy or Hasegawa J or L are seriously problematic, and stunningly difficult to build. Panel lines, twist in the tail feathers, sad cockpits, poor wheels.....having built both (but not yet the Tamiya - that's in the stash)....I'd rather give the Academy and Hasegawa kits away for free...and choose a different livery that suits the Tamiya offering.
Sorry mate....that's just the real deal. I prefer to choose kits that don't do my head in.

Remember White Lightning/Red Bull P-38 is not stock. It does have the early P-38 engine cowlings but it is otherwise a J. Except that it had no turbos in either scheme.

The best bet might be to kitbash the cowlings from an Academy E/F onto the rest of an Academy J.  Looks like the wings are the same so the parts should line up. 

You'd still have to remove the turbos from White Lightning and make a simple exhaust. For Red Bull, you'd have to build up a large scoop on top of the cowlings and still address the exhaust.

Hasegawa looks like an option too. It appears to be the same wing top for both the F and J kits so you could cut the booms somewhere under the wing and attach the F cowlings to the rest of the J airframe.  Probably doesn't have the J/L dive brakes either.