tank swap experience/suggestions

[dago dyna]

howdy. i'm planning on a tank swap for my 1999 fxdx (carbureted). the new tank dimensions are smaller in length, height, and width. the tunnel, if described correctly by the seller, should be spot on at 3 1/8" wide. i'm certain brackets will have to be fabbed/welded, but my question concerns venting. will a vent hole/tube need to be added? on my current tank there appears to be a small vent tube up near the filler hole once the gas cap is removed. also, will it be neccessary to run a crossover line? thanks.
attached is a small pic of the new tank:

 

[glider]

Very difficult to answer without more info.

Venting is done by the cap, the vent tube you describe sounds like the overflow line. The crossover probably will be needed or you will not use all the fuel in the tank if it straddles the frame to any extent which most do.

 

[dago dyna]

thanks glider - point well taken on the crossover line. but, is it absolutely necessary to have 1) venting?; 2) overflow tube? i am goin for a more clean, less clutter sort of thing as far as the looks go.

 

[glider]

You need venting in the tank or the engine will eventually stop. No air in, no fuel out.

The overflow will keep the excess fuel from going on you and the bike, your choice here.