You really only have three tensioning options from where I stand
1)Slotted engine mounts
2)Adjustable axles mounts
3)Tensioner- whether manual, or automatic
Sometimes, there's a fourth option. Depending on engine/jackshaft/axle orientation, you may shim the engine, jackshaft, or axle to tighten the chain. This will only work with the chain run in a vertical or near-vertical orientation.