I sure wish those Thunder Tiger planes would come back. That sorta P-51 was an outstanding plane and a perfect second plane.
CARR is correct, the LA .40 is about perfect for any of the .25 to .30 planes. I had a pile of the .40s at one time. Every trainer someone gave me had an LA .40 on it. I guess if it is a .40 size plane then a cheap .40 engine should be the engine of choice. That seemed to be the thinking anyway.
The .40 works on most any .40 trainer but there is zero OS factor in one. I pulled them and used the LA .46, a much stronger engine. The .40 is also the only LA I have ever seen completely worn out. But it would still run!!!
Back to planes again, any trainer the OP can get his hands on and I do really like the RCM trainer and the old Goldberg trainer. A CUB is a good choice too if the OP can handle one?