The guy who owns Old Car City at White GA (near Cartersville) on I-75 has a '41 Ford sedan delivery that has its original flathead 6 engine. Now the '41 sedan delivery carried over the '40 body and frame, so you're looking at the same set of clearance issues you have on your '39. '41 was the first year Ford had a 6 cylinder. The 6 was an easier fit in the cars which had a longer frame and engine bay starting in '41 and a flat firewall, and the '40-41 pickups had a flat firewall unlike your '39 but still essentially the same frame as your '39. Don't know how the length of the Ford flathead 6 compares to the 300, but I know it's longer than a flathead V8. So, on that '41 sedan delivery, Ford was dealing with the same basic frame and firewall you have on your '39. Here's how Ford shoed it in. The '41 pickup and sedan delivery uses a deeper front crossmember that is a one-year-only part. They also made a radiator cradle and radiator that is narrower and sits further up toward the grille.
The deeper’41- up front crossmember to clear the “G” series Flathead six would help a bunch. I have several and they can be modified to fit the ‘39 frame. These deeper crossmembers are exactly what you need to avoid cutting the firewall on 39/40 Ford’s with SBF’s
By the way I think a 300 six would be a killer engine for your 1939 Ford. Could never understand why they weren’t used more in applications that came with inline engines in the first place. I saw a Packard 120 with one once. Made a nice tidy swap. Back in the day the inline guys would’ve killed to have 12 ports, 7 mains and 300 cubes.
Guys in SoCal had 270/302 GMC’s in them in the early 50’s. Seems like a 300” Ford 6 would work too. I would make a deeper notch in the firewall just for convenience.
Yeah,GMC and Chev 6's were popular with some guys...Little known is the venerable 216 Chevy bored to the max at about 230 inches with usual cam, higher compression, better exhaust and intake could make a bit more power than a flathead V8 with the same mods..
Ok, here's what I wound up doing. I decided that I would put the 300 in if I had to take the body off the frame because of all the changes that would happen in the x frame area. The car is actually in nice enough shape that I really didn't want to take the body off, the only rust on the car was in the tail pan, driver's floor and some in the drip edge which was an easy fix. And I wanted to keep the stock (split bones) front suspension. At about the time I was going to pull the 300, a 326 Pontiac with a good st300 transmission fell into my lap at a price that I couldn't turn down. So I put that in. Having said that, I really wish I had used the 300, with the Pontiac I had to do some crazy things around steering box and column, motor mounts, fuel pump, exhaust manifolds, still had to get into the firewall, and a bunch of other stuff. Tight quarters. I think the 300 even with having to get another auto transmission (don't think there would be room for a manual setup) and converting from efi to carbs would be a more interesting combo. Probably still some crazy stuff to do if I had used the 300 but I think it would have been easier. Good learning experience though. Nevertheless, I still have the 300 for something else. I was planning to be driving it this summer but in the spring started having carpal tunnel, had them operated on and have about recovered from that, once the grass stops growing and I don't have to wander around 3 towns cutting it every week and then doing it again a week later (isn't that defined as insanity? LOL) I will be getting back on it and finishing it up.
Nothing to do with your question, but I have to chime in on the engine itself. Of the vast amount of vehicles Ive had in my lifetime, my 84 F150 work truck was the most damn dependable thing Ive ever had. That 300 did it all, easy on the wallet, it would tow and enough power for my get around needs. 127 thousand miles and no hiccups. I enjoy the thought of this "work horse" inline in a street rod. Good luck
Ford put a 6 cyl in the '41 light duty pickup and it was essentially your frame with a different front crossmember. Many have removed these crossmembers to install FH v8s. I considered installing a 292 in my '41 p/u, but someone had already removed the the 6 cyl. crossmember. I have the brackets that move the radiator forward and the accompanying hood latch. All works with a '40 STD grill and probably also a '39 DLX grill. Food for thought.
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