lining up output

[Leroy]

I have a 20 hp Onan where a 17 hp was i do not have the connection yet because im not sure of the best practice regarding that proceedure. THe 20 hp Onan is being installed on a Sovereign 7117 the exhaust is wrong and the frame had to be modified to fit the starter solenoid . there is a two stage air filter sytem that is going to make this unit look like a big-un. Question is do i get two 4 inch circles of 5 ply rubber conveyor belting and put a pencil through the center of them bolt em both up to there respective homes and attempt a line up that way? Leroy