There is very little difference between the P226 frame and the P229. Below is a picture of P229 parts in a P226 frame.
The only difference in parts between a P226 and P229 are:
- Grip screws
- Locking insert
- Hammer stop
- Guide rod
- Recoil spring
If you would like to build a 226 with a 229 slide, use a 229 drill jig on a 226 frame and it will take a 229 slide. You would want 226 grips and grip screws since your grip is a 226.
We like the longer grip of the 226 a lot. Our lead engineer uses this setup for his personal collection, 226 frame and 229 slide, so all parts are interchangeable with his 229s except the locking insert and hammer stop. He uses 226 mags in both.