It looks to me like the ramps are very steep, More that the driveway behind the rear wheels. So it would be trying very hats to roll down the ramps.  I'd at least chock the rear wheels. I also agree w/ kerndog on the ramp design. Not how I would have done it, but if it works...
CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax
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