If you have the itch before your parts show up you can build your own gutserts. Take you calipers to a big box home improvement store and start measuring. Lots of different things you can make them from. I've used metal conduit (will eventually rust), plastic sprinkler riser, schedule 80 met, and a bunch of other stuff oddball stuff. Drill a 5/8 hole through it, or ream if its close enough. Or whatever size hole you need for your guts.
Have a short piece of acrylic laying around? Same thing.
After the bore is right turn your step (glue surface) and then oring grooves.
Purchased gutserts are a great way to get the same thing every time and are just easier.
Have fun and don't be afraid to tear up a few sets of guts experimenting.