You could always find a nice T-18 or T-18A, that would be killer with a 360. My '77 is getting my T-18A out of my last Jeep that is no longer with me
but will live in spirit, as it was a '77 also, and this '77 is getting many donor parts, most importantly the T-18A.
You'd have to change your skid plate to the '76-'79 style, and driveshafts, and either use the Dana 20 TC or do something funky to adapt your Dana 300. Dana 20 is fine unless your really beating on it, I have no experience with the 300, but my 20 has help up beautifully, shifts smooth, etc.