They are esentially the same thing. The Sp-5's are slightly longer and need to have the seal changed before you even ride them. I have a a set of 70 forks with heavyweight springs and 20 wt. oil and they were awesome. Soaked up everything I could throw at them.
They are the same but the sp-5's have longer dampening rods that give you 1" more travel.You will be happy with the 70 forks with heavy springs and oil.I ran a set for about 4years and loved them and they are still going strong for the guy I sold the bike th and you can buy the dampening rods for the 70 forks if you want.