Nippon's 950 GH 5 iron shaft is 37.5 inches and length decreases .5 inch for each higher number iron. Other iron shaft manufactures may be longer (i.e. there is no standard before head installation) but all are cut to length at the butt end and generally have the .5 inch gap between irons. Titleist's 5 iron standard length is 38 inches with the head installed but before grip application- cut the shaft with installed head to 38 inches and the grip added will add 1/8 to 1/4 inch for a finished length of 38-1/8 inches to 38-1/4 inches . These comments assume the shafts to be installed are .355 tapered. Parallel .370 shafts are one length and cut accordingly to the iron receiving the shaft whereas each .355 tapered shafts is specific to an individual iron head. Not sure this is of any help to you but would caution that installing shafts without consideration of the shaft weight, head weight and grip weight in combination and their contribution to the final weigh and balance of the club may result in an ill fitted club.

OK, I'll take a shot at this, but I am NOT a professional club builder.

When I look at my 716 AP2 irons, the insertion depth and 1st step dimension is the same on the 9 iron and P. I am 95% sure that the shafts are taper tip (0.355" taper) That would seem to indicate the shortest shaft length is the same shaft used in both these clubs. If you use DG AMT from Golfworks, this raw shaft length is 37". As you build each numerically lower club, the raw shaft length should be 1/2" longer, so the 8 iron shaft should be 37 1/2", the 7 iron shaft should be 38", etc. This is for standard builds, not a soft step or hard step build.

When you look at the shafts, stacked vertically on the tips, you'll notice that the first step will start 1/2" higher for each incrementally longer shaft. If you aren't sure what I mean, compare your current set of clubs (with matched shafts) after placing the heads on a bench and setting the shafts to stand vertically.

When you begin to prep the new shafts, make sure the hosels are clean from old epoxy or other matter (some manufacturers have weights inserted in shaft times), prep the shaft tips using a belt sander to break the surface chrome and rough the section that will have epoxy bonds, and test fit the shafts in the hosels to ensure they bottom out properly. Once convinced that everything is properly prepared, then set the new (or reused) ferrules onto the new shafts. Mix epoxy properly and thoroughly! Make sure the shafts are properly set using plenty of the epoxy when installing, wipe off excess epoxy from the joint, and set the club in as near a vertical position as possible. When the epoxy has cured, cut the final length of the clubs from the butt end, and install the desired grips.

Golfworks has a printed club repair guide in case anyone wants to read and see photos of the processes for various repairs.

wow thanks for all the help guys I really appreciate it. I am installing C-tapers in the 5-9 so I guess I will just butt trim them to the standard length listed on titleist website after I install the heads back on, thanks again!

The C-taper 5 iron shaft should be 39.5 making the 9 iron shaft 37.5 so once matched and installed to the appropriate heads as per Thomas's instructions your plan to butt trim to Titleist's web site lengths should be perfect. If the swing weight isn't quite what you want you can adjust by a change in grip- a 4 gram reduction/increase in grip weight will increase/decrease swing weight 1 point