[smuzz]

I have the P-47, The Corsair and a Spitfire. I've not yet unboxed them so I can't say how much room is in them or how they are set up. All I know is that there is a stick mounted Brushed motor and gearbox (no speed controller) in the planes already.

Yeh, well I'm only guessing that there'd be more room within the Thunderbolt and the Corsair cowl spaces - I've not seen them in the flesh. Yes, the stick-mounted, brushed and gearboxed motor is what I found in the Spitfire too, and I expect them all to be like that.

I'm assuming that what I want to do is check the brished motor/gearbox and drop in a stick mounted el-cheapo HK brushless motor.

Well, that would be the easiest option - if you can find some stick-mounted options that offer a suitable power range. Have you checked Leaderhobby? (Edit: see post below) They might have something which could save a lot of mucking about.

I'm not much worried about the scale look of a $13.33 airplane so I'd be happy with any prop that suits but that'd be determined by the motor.

Yeh, OK.

Is there a standard/simple way to turn a stick into a firewall?

Put a cutting disk on to the end of a Dremel and use that to swipe the stick off, flush with the foam that it protrudes from. Leave the rest of the stick embedded in the fuselage, but keep a reference to its position (perhaps some felt-tipped pen markings in suitable places). You can then load up a plywood plate (perhaps a disk about 50mm diameter) with hot-melt glue or araldite and whack it onto the foam at the back of the cavity inside the cowl. After the glue has dried, you can put a single wood-screw though the ply and into the remainder of the embedded stick, just for good measure. Now you've got a plywood plate on the firewall onto which you can use woodscrews to attach the motor mount. You might need to provide standoffs of suitable length though, if your replacement motors are shorter in body-length than the original arrangement. The standoffs can be easily made out of more sandwiched pieces of ply with holes drilled through in suitable places to save weight - they can be glued in a stack until you've got the correct overall length. With a larger model and motor I wouldn't be that keen on just using woodscrews into timber as the motor fixing, but with something this size it will be alright of you use screws with a bitey thread.

One thing to make a note of beforehand - check to see if there's any down- and right-thrust on the motor mount before removing the stick. If so, it might be a good idea to replicate that with a replacement setup. Mind you, with the GuanLi models, anything's possible - it might not have any thrust-line adjustment even though it may need it, it's impossible to say.