what size engine or tank do you have now? the typical used front mount (I think its 2 quart) tank was redesigned around 1970, they offered it with center or front fill. they offered them that way 1970 into the 90's.
I think this was the only size/style tank where it came in right side fill. pretty sure they made mounts to work with all the small frame and some of the smaller horsepower medium frames that were typical in recreational use.