You can get them all day long around here for $100. 14FF are usually $150-300 depending on the gears (occasionaly they go for $100 too). I believe the only stock 60's to have 35 spline shafts were in the front. All the rest were 30 spline (I could be mistaken but I am pretty sure I'm not).
There were some semifloat Jeep pickup 60's with 35 spline and 5 lug pattern. I've got one waiting to be shortened should I break my 44 rear in my CJ-6. There were some hd model full float 60's with 35 spline but couldn't tell you what they came out of. I've gotten a couple of them out of core piles but have had a hard time finding 'em lately. Nickmil.
I have a Dana 60 FF, 35 spline rear sitting in my garage. Pulled it out of an older Ford van; the pick n pull had a sale, any rear axle assembly for 19.99 Couldn't pass it up. Don't know if I'll ever use it, that sucker is HEAVY! Right now, it's just cool to be able to say Yeah, I got a 60 in the garage.