I *think* '85 was the first year of hydraulic. The pedals bolt in, but you have to drill two holes in the firewall for studs that protrude into the engine bay. The studs both reinforce the pedal assembly mounting, plus provide mounts for the clutch master cylinder. I was going to use older stuff until I found a hydraulic setup. The old stuff fit fine in my '86, but it didn't even have the dimple in the floor for the mech. style clutch pushrod. I like the hydraulic quite a bit. Besides being slightly afraid of the bellhousing slave cylinder ear breaking off, I don't see there being much problems with it, besides the cost of rebuilt slave/master cylinders, which are kinda pricey.
Dorian
My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>