DODGE VAN 318 - 360 -400 - 440 can i use it

bore x stroke on a 360 is 4.00 x 3.58 - 340 is 4.04 x 3.31.

Very unlikely you'll find a 340 in a yard. Better bet is a 360 from a donor vehicle, these can be had in vans, trucks, and older mopar passenger cars. Be sure to get a running specimen if your intention is to flop it your car without doing much to it.

If you get a truck or van motor you'll have to change the pan and oil pump pickup to a passenger car version, and the pan will have to come from a 360, the pans on 273/318/340 are the same, 360's are unique due to the rear main bearing cap size.