Wow, steady on. Work with me here. The key intake valve size "ceiling" is 0.49 per inch of bore, and even the 200 or 250 over bored to 3.74", the 1.83" items used in most later GT 40 302's will be too big.
I've seen early 308/304 valve sizes used in the 2V 250, and I certainly wouldn't be using Chevy Fuelie or L34 308 valve sizes. (1.92 to 1.94" intake).
There are about 12 things which influence ideal valve size, and one of them is how much increase you can get on lntake and exhast on the existing head, and not get failure with the cam, block, piston.
The basic precendent for this engine is a character halfway between a 265 E49 and an HX cammed Holden XU1 202. There is an extra 50 odd cubes to that Holden. Both were race combinations with a wild cam and imroved head flow on the cooking variants.
On those little 202 engines, the cam was a screamer, and yet it had quite small valves, poor head flow and didn't ever need to go any bigger than stock 308 V8 valve sizes. So little 1.675 " inlets and 1.45" exhasts on a 3.625" bore was just fine up to 216 hp net at 6500 rpm with CD 175 carbs, and 245 hp with Webers. It was only on Yella Terra ( and some aftermarket Superflow) heads that 1.74/1.50" and 1.78/1.55 valves could be used. That was with 3.625" bore, so the key intake valve size "ceiling" is 0.49 per inch of bore. Same with the old Valiant 265...1.96" inets on a 3.91" bore but with a radical canted valve hemi head, and the key intake valve size "ceiling" is 0.50 per inch of bore
Truth was, in a 202 XU1, the valves weren't the limiting factor in the head flow, it was ports and piston size.
When you've got a great large port head like the Ford 2v has, and 25% more stroke and yet still shove a big ass cam in, you'll find the GT40 and XR/XT GT valve sizes, or 351W GT 4V are too big.
So my call is that the 250's long stoke will deaden the camminess of the engine, but the bigger than XU1 and similar to E49 ports will then make the engine quite cammy again. If you enlarge the intakes, you have to balance the intake to exhast flow, and there may be an issue with how big the exhast ports and valve can go before issues with valve seat failure occur.
