Aluminum master cylinder question

I'm replacing my master cylinder ('70 Cuda) with a later model aluminum version. Can I use a parts store replacement ('88 Diplomat would work)?
Or do I need to spend the extra $ for Doctor Diff's version?
What are you guys using?

you would just need the right bore dia & if manual brakes, that the rear piston cavity (the thimble) has a circular recess about halfway down into it for the pushrod neoprene nub to lock into (PB can work with or without the recess)

Mine does have manual brakes. Seems like the brake light switch would not allow the pedal to come back far enough for the pushrod to ever disengage. Thoughts?

Check with Dr. Diff (Cass) . . . he knows all !

Get Cass's input and then you can make an informed decision.

Parts store is fine, plus you get lifetime warranty.
Brake light switch is on a bracket that's adjustable.

I assume that if you buy the smaller bore master from Cass, he has already modified the piston for the push rod/retainer?

That reply gets saved in my "Moparts Tech worthy" threads

the alum MC's will have a different base flange thickness and the piston will likely be at a different depth than the OE iron MC plus you'll likely use the 4 bolt to 2 bolt adapter plate all of which will affect pushrod length needed so figure you might be needing the MP adjustable pushrod after mockup

Dr Diff will set up the right stuff for you.

I went with the 85 Dodge Diplomat MC because I actually have 10 pistons in my brake system,Wilwoods on the rear and factory discs on the front.
The tech section on the Mark Williams site suggested a 1" bore with the brake system I'm using. I'm probably going to finish my brake upgrade this weekend so I'll post back and let you know how it fits.
Gus

Eberg once made mention of filling the cavity with RTV to lock the pushrod into a piston without the manual brake recess. At first blush it sounded hokey but with more thought I think it'd be secure & Eberg has forgotten more tech than I will ever know

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