My daughter is moving to Woodland Hills from TX next month, will it be legal for her to bring her custom Glock 17 with grip reduction and TSD red dot slide (changed the barrel out to factory unthreaded)?  Should she send a photo of the gun along with the New Resident form?

Edit:  This flowchart I found at calguns.net seems to clarify things.  It appears she'll be legal.

http://www.calguns.net/caawid/hgflowchart.pdf

No 10+ mags and no threaded barrel. Rest doesn't matter.

If she's moving here permanently, CA will be her home state of record, the state law says she needs to mail in the registration and fees for her pistol, IIRC it's within something less than 30days.   The CA DOJ Firearms Division FAQ page has the info.

The roster only applies to buying guns from an FFL. It doesn't limit what handguns she can bring into the state with her or limit customizing her guns.

No need to send a picture. The form is pretty simple - manufacturer, model, serial number, caliber, and purchase date. They didn't seem too picky with mine. I brought a stripped 1911 lower so left "caliber" blank, didn't have a purchase date for any of the guns I inherited, and don't even remember what year I bought my Kimber so left the purchase dates blank on about 10 of the 23 guns I had to register. They didn't question any of them.

I did send a picture but that was for a Yugo SKS to show the grenade launcher had been removed. I took the picture in a dimly lit storage locker with an old phone. You can't even tell what's on the end of the barrel in that fuzzy picture but they didn't question it.

Just make sure she gets the form submitted within 60 days and modifies/replaces mags that hold more than 10 rounds. She can buy magblocks from magazineblocks.com to avoid replacing expensive magazines. A magblock is a plastic insert that goes inside the magazine to block the follower from allowing more than ten rounds. They're pretty cheap, about $5 each.

Do you only need to register if you live here permanently?

Have her buy as many off roster handguns as she can and then bring them all in.

Seriously.