Dude, you can park right at the bottom of the climb, just before the first "wall". View the area in google maps and when you zoom in you'll see Becker Rd. intersecting W. Saugerties Rd./Platt Clove Rd. Make a left onto Becker just before the road shoots up about 10% grade. There's a little parking space for about 5 cars along a fence for a hiking trail access pt.along the Plattekill Creek. Likely you may see a few cars already parked there and if it's on the weekend, the spaces may be taken. Go during the week if you can.
Take this with a grain of salt (you may be in better shape than me) but I basically DIE on this climb in a 39-28. Be warned, descending is almost as brutal (but a lot more fun) as climbing. My arms feel like jelly and they're pretty cramped by the time I reach the bottom. Keep your speed in check, you'll have to break hard on some nasty hairpin turns which can sneak up on you. Also, pavement is VERY POOR which isn't an issue so much when climbing but when breaking hard on the descent while you're being jarred and knocked around by ruts and loose stone, you can see why my arms are tired. I don't descend anymore because I looked at my rear Mich Pro 3 Race tire recently and the outside rubber layer was all chewed up to the threads. My best guess is this happened while having to brake hard on the bumpy jagged pavement.
The Mead Mtn.Road is also a great climb but I'd rate it a fair bit easier than Platt Clove. Not familiar with Glade Hill Rd. but I'll have to check it out someday.
Take what i say with a grain; this is my first full season but for me Platt Clove is the definition of "pure suffering." Have fun, man!!