I am assuming that most states prohibit using original plate glass in the windshield. Been looking at the vendors that sell the channel that beds the safety glass in the frame. They are so expensive. Are there cheaper alternatives?

If the brass channel is good in yours, just reuse. Maybe not states, but most every club prohibits plate glass in the windshield and side windows. Some may be a little more lax in checking then others. Good idea to change it out, my and many others OP, it's just plain stupid to drive with plate glass.

I took my frames to the local glass shop in Hillsboro, MO (population 2635) and let them replace the plate glass with laminated glass using my existing channels. They did a great job for around 100 bucks.

I would like to do mine however I seem to remember that today's glass is slightly smaller in thickness measurement making it loose in the original channel. Is this still correct?

The new glass is, as1 and as2, as2 is thicker If I remember right, as1 for side or rear glass, as2 is for windshields by law. Check it out, glass for my coupe, all seven pieces was just $250.00

There was a reason Henry Ford changed to safety glass for the second Model A's windshield. There was an accident on the test track where the test driver went through the plate glass windshield. Henry heard about the accident and resulting injuries and decreed use of safety glass only in the windshields.

Every state may have their own variation of the law.
The Province of Ontario states " IF the glass has been changed, that replacement must be of safety glass"

Your insurance company or club affiliation may insist on safety type glass.

I think speedway is cheaper, still its 200 bucks.
http://www.speedwaymotors.com/1915-22-Ford-Model-T-Brass-Glass-Setting-Channel-f or-Open-Cars,39102.html

I changed it in my A models because I drive them a lot and the new glass looks good. I put it in my 26 rpu because it was busted anyway. I think most glass shops will cut from a pattern at a better price. Tim

I had a flat glass guy cut and install mine. Was cheaper than at the automobile glass place

When a shard slices through your eyeball and pierces your brain it's very disappointing. Change it.

Mark, I agree that the channel is very expensive. I took my 1914 windshield to a local glass place and they replace it with safety glass using a thicker channel. Can't tell the difference between the old channel (unusable)and the replacement.