that shop manual pic is misleading, note the offset jog in the middle of the pin where they "photochopped" it .... mounting the front that low would give problems with misalignment stresses on the rear mounts and the trans angle to the front U-joint
what's the V8 you're trying to install? do you have the correct engine brackets? are they in the right place?
the mounts from the vendors are correct and work fine in any 56-58 I've put them in with 283's and 350's, there will be a problem with clearance for an HEI, but the stock valve covers shouldn't be touching
Bill
