You're probably right. I've read all I can find and have accumulated quite a few parts but the only transmissions I have other than manual ones are the ones with the barbell style weights.
I'll see if BJM or his son has one we can measure early next week if you don't get an answer before then.
Attached is the picture of the weight I measured.

Huston
hgonthehd

I picked this Simplex up last week. You all probably saw it on EBay but it didn't sell so I sent the guy a low ball offer and we came to terms.
Frame # 13314 which I think should make it a 1956 or 57. Brake light switch tab is on top of the lower frame.
It had a J motor on it with an iron cylinder. All incorrect for this bike.  Motor number J6223
I have an extra M motor and transmission but what I like about it is the paint is all original and I plan on leaving it that way. A PO had put Sportsman Stickers over the original Simplex Automatic decals, I was able to get the Sportsman stickers off with some sticker remover and lots of care leaving at least a sign of the original Automatic decals.
The rags in the gas tank are wicks in case I get to mad.

Huston
hgonthehd

The thread started with the new seats from Heathers Leathers then went into old original seats and then to the new plastic covered ones.
I must have all the dirt out of the original larger seat cause I've used a lot of saddle soap. I have some mink oil that I will start working into it and see if that helps it out.
Here's another picture of the old larger seat I'm referring to.
The article from the VMBC posted on this site states at some point prior to 1944 an optional larger saddle appeared that required an adapter. I got the adapter with this seat along with a couple other goodies.

Huston
hgonthehd

I thought someone put one of my bikes on EBay but it is just it's twin.
He says it's a '53 but the motor number looks to be around '56.

Item # 121502589466

I'm anxious to see what it brings.

Huston
hgonthehd

Bill,
 I just missed you at Billy's last Saturday. I told him I would clean the basement out for him.

Huston

I'm pretty sure it's not a '48. It has a flat brake pedal and the '48 had the round peg, the crash bars look like they bend down slightly from where they attach under the frame until they downturned on a '48 they ran flat out to the downturn.
Does the tank have dual gas caps?

Huston

Rick,
 The info I got from BJM was more related to the mounting plate they used. They welded theirs in place and I would like to make a bolt on mount plate so a person could go back to an original motor if every desired. I've worked out a pattern and will try to get it cut out next week.
I'll post more as I work my way through the flywheel and lighting coils also.

Huston