Using P229 Parts in P226 Frame
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:
Slide and Barrel (guide rod and spring too)
If you would like to build a 226 with a 229 slide, you would want to buy a 229 drill jig and specify that you want it modified for a 226 since the 226 is a tiny bit longer at the rear than a 229 and won't fit in a 229 drill jig or the older 226 drill jigs.
If you already have an older 226 drill jig that was made for a 229 frame, it would need to be modified by sending it to me or doing it yourself with a Dremel. Below are some pictures of the procedure: