A 45 of the same make as a 40 will be built in the same case, ergo the 45 will fit. Generally all 45s and 40s are interchangeable installationwise with the exception of the mounting holes. Generally you won't notice the difference in power except for cases where the 45 is specifically a high performance engine and the same manufactures 40 is a sport 40.

A 5 to 5.5 lb airplane will be no problem for any 40 out there. For your application I would focus on running reliability and ease of operation. The TT42 with it's airbleed carborator would not be my first choice. But if you have it running with a high degree of reliability in another plane, then use it.

Denis