If your particular build works out that you don't need to take any slack out of the chain then you won't need to use a tensioner. BUT, the new chain will stretch and you will need one eventually. Some guys have had success using shims in the engine mount to take up the slack in the chain and therefore eliminating the need for a tensioner. Shifting the engine forward has double the effect tightening the chain. (ie. move the engine forward 1/16" and you get 1/8" tighter chain because of the top and bottom runs of the chain are both effected by the 1/16" movement of the engine.