I can't speak to GSSF. For IDPA, you'd have two options: shoot either in the SSP (Stock Service Pistol) division, or in the ESP (Enhanced Service Pistol) division.
SSP is where you'll find the vast majority of Glock shooters because ESP can include single-action-only pistols. The pertinent IDPA rule for SSP:
Rule 8.2.1.3.3 wrote:Magazine releases, slide stops, safety levers, de-cocking levers, hammers, and triggers, that are stock on one SSP legal firearm may be used on another SSP legal firearm from the same manufacturer provided they are drop in replacements. Parts in this list must come factory installed on standard production firearms. Special parts that are available installed only from a factory custom shop are not eligible in SSP.
You can
barely get away with dropping a standard G34's trigger assembly into a G19 in SSP. The reason is pistol size. SSP guns, with magazine inserted, have to fit in a box measuring exactly 8 3/4 inches by 6 inches by 1 5/8 inches deep. The standard G34 is 8.81" long and will barely fit in the box if you angle it perfectly...SSP legal by maybe 100th of an inch.

The G34 Gen4 is a fraction shorter at 8.74" long, so it drops right into the box.
All pistols that are legal in SSP can be used in ESP. Several modifications are legal in ESP, though, that are not in SSP, including triggers: "8.2.2.2.5 Action work may be used to enhance trigger pull as long as safety is maintained."
Join the NRA or upgrade your membership today. Support the
Texas Firearms Coalition and subscribe to the Podcast.
I’ve contacted my State Rep, Gary Elkins, about co-sponsoring
HB560. Have you contacted your Rep?
NRA Benefactor Life Member