I think this project is intriguing, so I did a little research. There's a 1/32 B-25 made by HK. It has R-2600s. They are twin row 14cyl engines, but the way the kit is made, it wouldn't be a huge problem to make a single row 7cyl. Expensive kit, but maybe someone at Aircraft Resource Center or Large Scale Planes would part with one engine. If that doesn't work out, Williams Brothers made/make several 1930s racing planes with an R-1340; a single row 9cyl engine. If you can live with 9 cylinders, that may be the way to go. Those kits are cheap enough to buy just for the engine. They include the Gee Bee planes, Laird Super Solution, and Hall's Bulldog.
I've got a pair of resin R-2800s somewhere around here. Will trade for a kit. I'm into street rods, lead sleds, and pre-war coachbuilt classics...but I have pretty much every pre-war luxury car ever made into a kit. Would love to have a '26/'27 T Coupe (if one is available) or an AMT '32 Chevy roadster. The R-2800 is a twin row radial, btw. Engine from the F4U Corsair and P-61 Black Widow, among others.
Are you polishing the pewter parts? I had one of these years ago and filed/sanded the air cleaner into a teardrop shape, then it polished up like chrome. Maybe drill a hole in the mating surface of both parts and jam a piece of plastic rod in there to help hold it in place.
In the "standard" 1/24 scale, you can get a slot car made by AutoArt. I have not seen one close up, so I can't tell you how detailed it is (or isn't). It would likely be easier to add detail to it than a diecast metal model.
Ian- Check with Aardvark Models. They have a hood and engine parts for a naturally aspirated Duesenberg J. It has the arc-shaped louvers on the hood sides like Greta Garbo's J. There's one on ebay right now. Just misspell the name as "Deusenberg" and you'll find it. I believe he has a couple of bodies for Duesenbergs in the works.
If you don't want the hassle that comes with discharging a firearm, look into big-bore air rifles. They are becoming more common, with prices falling. I have a Benjamin Marauder in .25 caliber. It operates like a bolt-action with a rotary magazine. It is the pre-charged pneumatic type, with an on board 3000psi air tank. The Marauder is available at a good price and can be tuned for more power. You can also re barrel it to use cast lead bullets for more knockdown power.
Of course, a better fence will protect your pets without need for armed overwatch.