89 mighty max

i have a 89 mighty max with the factory G54B in it i would like to do 4G63 swap to beef it up i have a lot of questions.I am new to the Mitsubishi seen and love the truck can it be bolted to the original tranny?Any help is welcomed and wanted.Tks

I have a 1991 Mighty Max and with a new air meter sensor on it. The exhaust manifold gasket has leak at the engine block. The code is showling a bad air meter, but should it be a bas O2 sensor instead ?