The Ford Small Block Six 250 uses the same SBF V8 - Bellhouse, Clutch tranny , mini starter, etc.. . The 250 can use the same 157 tooth FW (Neutral/internal balanced). My D6DE block 250 uses a non-cable C5DA 157T SBF bellhouse , SFI Flywheel, Centerforce Clutch to a Cobra T5-Z spinning the 8" - 3.80 Posi gears for fun. Of course setting up an automatic car with the pedals, clutch linkage and shifter is more fun, needing a donor setup or serious fabrication.
The earlier 250 Maverick required automatic trans(no idea why, Fairlane & Mustang had 250 & three speed stick since that engine was introduced in '69)... By '73 or definitely '74 the 250 was available with stick shift(had one)... s already mentioned the 302 all use externally balanced flywheels, so even though it fits 250, cannot be used...
You could use a flywheel and bell housing off of a 240 or 300 six. They have the neutral balance on the flywheel. They are the 164 tooth flywheel and they use an 11 inch clutch. I've got a 250 in my falcon and am using a 1984 f150 bell housing and flywheel. The trans is a 3 speed top loader from a 66 mustang. I've been down this road with my comet when I converted it to stick. I used a bell from a ford Econoline. One other thing you need to remember is that the starter us different for the 164 tooth flywheel. You can also pick up a t5 from a mid 90's mustang with a v6. They use the small block bell bolt pattern. They are also 164 tooth flywheel bells and have a neutral balance on the flywheel.
