Kitbash a P-38 question

Personally I'd say go with a Hasegawa H & L for such a project. Their engineering should be similar enough to reduce major fit issues. Especially where some contours may come into play. Using kits from two separate makers increases the likelihood of such problems.

Building a model of the Red Bull's P-38 which is an -L variant (Wings, pod, and booms) with -H cowlings and some other mods that were done to the supercharger and exhaust system. So I need remove the cowlings and replace them with the -H version. 

Why would you need do this when decent kits of the H already exist?  You would also have to change parts of the outer wings, rear booms, interior, and canopy.