Thanks very much to all you Y-BLOCKERS for the Info. I found a vendor who sells tips for the push rod.

I have a Wilwood dual-reservoir mc for my 55 Tbird, but I haven't installed it. However, I determined that I could not use the pushrod from the original 55 mc, and the pushrod that came with the Wilwood mc was too long, even though adjustable. I ended up shortening and re-threading the Wilwood pushrod. I'm still not 100% certain it's correct, but I think the pushrod for the 1st-gen Mustang would be, as already mentioned. 

By the way, the original 1955 mc has a 1-inch piston. The same is used for both manual and power-assist. However, Wilwood recommended 15/16ths for manual brakes, so that's what I bought.  

Please let us know how it works out. For a full size car Wilwood recommended a 7/8” MC without vacuum assist. The foot pressure is a little less than 4 drums. I also installed an 8.8 rear with F-150 wider drums and shoes. The brakes were from a power brake truck with 1-1/8” wheel cylinders. At their recommendation I went to 15/16”. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.

I neglected to say that I put Wilwood Dynalites on the front but retained the stock rear drums. I had put larger single-piston Lincoln calipers up front and Stainless Steel Brake Corp. rear discs on my 1988 Mustang 5.0. The larger Lincoln calipers were a noticeable improvement, but I wasn't impressed with the rear discs. Unless you're road racing, doing a lot of mountain driving, or spending a lot of time driving backwards, it's better to upgrade the front brakes.