Honda-SOHC

In the process of rebuilding a supposedly totally rebuilt 1972. 500. (think I've been fleeced!!) When I rode the bike briefly the front end felt rock hard. Played about with different fork oil and check that everything was straight. Today I removed the fork springs which measured 480mm in length. According to the manual they should be around 425 to 450mm. Plus also there is no long damper rod in these forks making me think there later forks. Would I be right in this assumption?? I've also ordered some progressive springs from Bike Barn as my previous order with Performance Parts never did arrive after waiting nearly six weeks (buyers beware!!)