Hi Hendrick
I've made quite a few with internal and external stingers. Here is a link from Quickdraw that gives the demensions,
http://quickdrawengines.com/Page_191.html
I sell these for $210.00 plus shipping and silencers are extra. The T-Mod clamp on is $35.00 and the Quickdraw which is held on by springs is $40.00.
Hope this helps.
Don