I redesigned the 3DR Simple (http://trains.socha.com/2013/09/3dr-simple-delta-printer-part-i.html)end effector for use with a J-Head. I don't have a Printrbot Simple hot end and had a few J-Heads on hand. This particular design is for a TriDPrinting.com J-Head. My MakerFarm J-Heads are slightly different, for instance, and will require a different mounting plate.
3 M3 x 20 socket head cap screws
3 M3 nuts
1 M5 nut
1 Push Fit Pneumatic Bushing for 4mm OD tube, 5mm thread
TriDPrinting J-Head (at least the PEEK body)
Print the new platform and the J-Head holder plate.
Use a torch or high heat to heat the M5 nut and then sink it into the hex recess on the top of the platform. It's better to have metal threads for mechanical strength. The hex recess was purposefully printed small to allow a very tight fit with heat. You must use heat because the recess is too tight for just a press fit.
Assembly the J-Head, mounting plate and platform together.
Install into your 3DR Simple and enjoy.