congrats on your first war bird I also have a H-9 P-40 with a OS 91 fs here is a few tips to pass on your way .
first is make sure your engine is well broken in and running smooth,and you radio is properly installed you need a retract servo also if you havn't got one yet.make sure the retracts don't bind if they do they will run your battery down fast.
I would also recomend a 90o close header for keeping the pipe out of the cowl you can route it out the back and you will not need to cut the cowl I will in close a couple a photos.
a remote glow plug igniter is also needed as well as a fuel dot or a Dubro remote fueler you won't be able to get to your engine with the cowl on .go slow with cutting the cowl .
replace the rear push rods with stiffer ones the ones provided in the kit are super week and can bend under stress the ones for the ailerons are so short you shouldn't have to .
and most importantly have a well seasond pilot check out your bird before you even think about flying there are allot of parts to a warbird