Dual gas tank switching problem

[dyno]

Hi,

I've been fighting my dual tank selector valve on my 1980 K20 for years now. The valve has 6 ports; 4 in and 2 out. I have searched everywhere and cannot find a replacement valve that has a single wire like mine. All 6 port universal replacement valves have a multi pin connector.

So, my question is, what's the purpose of the extra 5/16 line on each tank? Could I cap those off and use a 3 port valve?

Thanks.