Engine Swap 454 to 6.5 diesel

[kape]

Hello, My project is to change my 454 gasolin engine to 6.5 diesel engine. (Thanks my goverment gasolin taxes.)
Couple of issues coming on my mind: How those fuel return line should be shorted out, because my car has double gas tanks. Example, i choose driver side tank to feed fuel to engine, and return line is connected passenger side tank (or vice versa). Can this happend? Few months driving ,engine feeded only driver side tank--> passenger side tank may overflow?
Do i need some valve , powered by same wire as the original fuel choose valve to control return line feed.
How this is solved on truck with has originally diesel engine and double gas tanks?
Many thanks Kape