I have Updated this Older Post with some good news if you have converted over to a 12 Volt Electrical System with some more current Info on how you can use the stock Ford Distributor's!
Welcome to the best Ford Six Forum. Many people in the past have swapped in a number of different Distributors like the flathead or later model six cylinder MoPar, the 170, 200, or 250 (1969 up), Ford Small Six Engines form 1968 up to 1974 for a point type or if you have converted over to a 12 Volt System then you can also use the 1976 to 1983 200 / 250 Six DuraSpark II Electronic Ignition system , or a 1960's, 1970's etc. GM Six Point or Electronic Distributor (if you have also converted to a 12 Volt System) essentially modding the shaft and Distributor body as is needed to fit into your 226 or 254 Flathead Six. In general any six cylinder Distributor that turns the same direction as the Flathead Ford Six and has a centrifugal advance (with or without a vacuum advance) could be made to work plus going with one that's also a later model electronic system also helps. Most of these distributors with the exception of a MoPar flathead six will also need to have their advance recurved / modded too.
The flathead Mopar distributor's are the correct diameter to fit into the Ford Flathead Engine's. You just need to cut the shaft off of the Ford and weld it together be sure that you match the total length of the existing Ford 226 or 254 Flathead Six Distributor, then you will have a good mechanical advance. Most any Dodge Plymouth or Chrysler Flathead Six can be used for this swap there are couple different distributor types but are all the correct diameter. However if your want to use a Pertronix in it make sure that that model distributor is one that they have a unit for. If you going to use it with points or the later Mopar Electronic Control Box Swap below than you can use any of them all the way up to the early 1960's Flathead Six's (Pre OHV Six's) and that way the Advance Curve is going to be near perfect as is. Check the below Post and link for some excellent additional info on these type Distributor swaps in an older post by site member "Flatfords" who did one of these distributor swaps on his!
If you have also converted your car or truck to 12 volt system there is another upgrade that is a very simple way to go for an Electronic Ignition System using one of the 1973 up MoPar Electronic Control Box, this can be used on any 12 Volt Point Type Ignition system and on any engine. I used this method for over 37 years on my old 1956 F350 (1965 425 Old's V8) the points don't have much current going through them anymore so they don't get burned up or need to be changed. I am not going to type up how I did this since there is a good write up already online that you can find at Go Fast for Less.
https://www.gofastforless.com/ next click on Electronic Ignition it has all the directions on how to do it.
Update
There is now a new Part for a reasonable price that will let you keep your old Load O Matic Distributor (this works on any Ford Distributor) and now turn it into a Programable Electronic Ignition. All you do is lock out the old Distributor's Advance System. Details are here in this Link.
https://www.cbperformance.com/product-p/2013.htm
As for carb's there are numerous ways to upgrade, and if you wanting to stay with a single or go to a multi carb system? Good luck
The Additional Info by site member "Flatfords"
viewtopic.php?f=18&t=21289&p=432661&hilit=DISTRIBUTOR+CONVERSIOn+226#p432661
Flatfords Quote from Mar.15. 2009
The points, condenser, rotor, and cap are the same in the mid 47 up H and M 226/254 and the 223/262. The easy thing about converting some other distributor to fit in the 226/254 is that the distributor shaft does NOT have the drive gear on it. The gear is on the oil pump and the distributor is driven by a spline in the oil pump shaft. Therefore, any distributor for a 6 cylinder that turns the right direction (clockwise from the top) can be made to fit by either turning down or sleeving up the part of the distributor that goes in the block. The clamp grips the top of the part that goes into the block. The drive shaft with the spline can be cut off of the Ford distributor and welded to the end of the new distributor at the correct length. The distributor gear on the new distributor can be cut or ground down for clearance as the hole in the Ford block is not very deep remembering, however, part of the gear is needed to establish end clearance for the distributor shaft. Almost any later 6 cylinder distributor can be used, the easiest maybe is the 6 cyl chevy 194 230 292. Also easy is the 200 cube Ford 6. Both used electronic ignition in the later distributors. See also Distributor conversion post just above this topic. Remember that a flathead requires about 10 degrees crankshaft less maximum advance than an OHV engine. The distributor will have to be recurved. Edited