Originally Posted by Salamandrine

Are you sure it fits? That's at least an inch more seatpost than should be showing. Not sure if that's your ride height or just where the it is now. If you're comfortable on that size, that's fine, but I'd suggest you install a longer modern seatpost. Vintage ones were short because of the sizing standards of the day, and if the post is raised too high the seat lug can break.

Mighty fine PX10 find for sure. That's about the cleanest one I've seen.

The stem and bars on these were pretty dubious, as others have mentioned. Stem is a bigger danger though. It might last forever with no problems, or it could break unexpectedly. Eddy Merckx swapped out his PX10 bar and stem for Cinelli...

Simplex derailleurs shift perfectly well if properly adjusted and set up. There are two problems. Not many people these days have experience adjusting old push rod derailleurs, and the delrin plastic is now 50 years old. The plastic portion of the front derailleur is in tension, and they will eventually crack because the plastic has gotten old and brittle and lost its tensile strength. People slag the rear derailleurs all the time, but I've actually never seen a broken one. BTW if anyone has a pic of a dead Simplex RD, please share. Surely someone has snapped one. There were so many...

One additional issue is that they are optimized to work with the gearing of the time. If a 14-23 and 45/52 or maybe 42/52 doesn't cut it for you, the Simplex derailleurs aren't going to be optimum.