RR tie ramps = fail. I'm sure the oily substance within that material is bound to seep out.
On another note, I gave my friend with the Mustang my original ramps. He didn't want to wait for me to nail some together, lol. So I made another set specifically for my Z28. I got pressure treated because I'm not lugging 30+lbs of wood for each ramp in and out of the house... and no, I don't have a garage.
I bought 6 pcs of 2x8 - 8' PT. I left 2 pcs whole (no cutting) and used those as the bottom level of the home made ramp. Then I cut 2 pcs of the 8' to 66" with 30" remaining. The 66" are used as the 2nd level of the ramp and the remaining 30" will be the top level of the ramp. Then I took the 2 remaining pcs of 8' and cut 54" to use as the 3rd level. The remaining 42" will be used as the 4th level of the ramp. Then I just cut a 3" pc off of another pc of PT wood I had at the house and used it as the "stoppers" on the top "step" of the ramp.
All in all, the Z28 is lifted about 7" or 8" off the ground. With the front wheel being at the top of the ramp, the bottom level of the ramp extends almost to the rear wheel. I had to make the bottom ramp 96" (8') because the height of clearance mixed with the length of the nose would have hit if I started with 66" @ 12" intervals.
Anyway, for long nose cars like mine, 6 pcs of PT lumber from Lowe's to be used as ramps cost <$35. & I already had a carton of 2 1/2" nails
I have pics of the car on the ramps. I'll upload tomorrow for all to see. So far she's been on the ramps since last Thu or Fri and she hasn't budged a bit. In my opinion, I'd trust these WAY more than any jackstand or jack. Just my $0.02.