SIG LT-40 Trainer and O.S. 46LA
The 46LA will be fine. I would say that the 40LA is too small but the 46 will work just fine. Having said that, if the hobby shop will let you return the engine and you can afford it, I would go for the 46FX. The difference in power is substantial and really helps. Like when the grass hasn't been cut in 2 weeks or a big wind comes up and you need the power to make it back to the runway. I ran a 40fx ON my LT40 and it was barely enough if the grass was getting tall.