The bike I bought had a V shaped bracket that mounted the back of the trans plate. I wasn't going to use them. I was gonna sell em if interested. or I can take a picture so you can see what it looks like?
Not sure how tall of a passenger you planned on having on the back, or what your pipes are like, but almost every old frame ive bought, has had peg mount tabs welded just behind the tube where you would mount your solo seat springs to.
Heres a few pictures. The last two shows how comfortable...ish it looks with them where they are.
I didnt take any of these pictures. most of them came from this board over the years.
First, what kind of bike are you needing to put pegs on, BT or sporty or? My rigid sportster has mounting tabs in a similar location as the pics above. I remember the first lady I had sit on the back when I was a kid, damn that was cool!
That V shaped thing is called a moustache bar, very common. Just sold one on epay with Anderon Pegs for $25. They are cheap, every grey beard has 2. If you don't want to weld your frame, it bolts to the rear of the trans .
Should come out right behind your clutch hub on the top, in the 1 o'clock position. Works with either set up & yer o'lady will be much happier with the position. Besides, her knee makes for a nice resting place for tired arms.