Constructing frames from scratch is a very tricky business. Have you considered the liability you would have to assume if your frame broke?

I'd suggest you approach some of the aftermarket manufacturers. They may already make a frame like you want, or one you could stretch. They could also provide the critical dimensions, which would be a lot easier than trying to get them off a bike on a shop floor.

Look at some of the mags, like American Iron or Hot Rod Bikes, etc. to pick up some names.

Liability issues are not a current concern with the bikes mentioned and I am avid chopper mag reader. Thanks for the reply.Still need the measurements though.

Here's a link to the motor mount dimensions,

http://64.172.168.34/neatstuff/motor-trans-mount.htm

But for the most part it is loads easier to beg, borrow, or whatever it takes, a Softail frame and build a jig off of that with the adjustability you need built into the jig.

If you have a local powdercoater you could try this. Assuming the powder coaters is reasonable you could offer to pay for the powder if one of their customers would lend you the frame?

I've tried to get factory drawings through my dealer, and never had a lot of luck. But from experience I can tell you that factory frames are all over the place. So maybe that's why it's so hard to get the factory drawings?

Mine has adjustable tranny mount fixtures on the jig so I can build offset into the tranny mounts which saves buying an offset plate.

Another thing to consider is that if you're using stroked motors then there can be clearance issues with the stock frame, which already has clearance issues as witnessed by all the flats pressed in to the tubes!

Not a lot of help I know but Hey! at least it's something.

I helped reverse engineer jesse rookes first frame, "Dinah".  He built it first, and then wanted to make a CAD model so he could make accuurate dupplicates of the chassis.  

http://www.jesserookecustoms.com

painstaking measurments and on the fly fabrication is how it is done!  

I used straight edges, squares, calipers, micrometers, and an angle-meter.  It took about five nights to measure out the frame.  Then it took another week to model up the frame in several variation in CAD.  If a measurement was found to be off or fined tuned during fabrication...the parametric model was changed to reflect that.  Hope that helps.

Regards,

Dion
P.S. I still have CAD models of the frame but under and NDA can not share files.  Sorry!