i Was Gone To Build My 70 Chevelle For The Street But Went Towards The Track. I Bought My Ford 9 Rear To Go With A Mild Bigblock. But Now I Went A Different Way. The Bigblock Has 600hp And The Guy I Bought The Rear Off Of Said That It Has A 31 Spline And Only Good Up To 400hp.and Im Takeing The Posi For The Street Out And Putting The Spool In And He Said It Would Make It Stronger.but How Much.this Is A Foot Brake Car .no Trans Brake.do You Think The Rear Would Stay Together Or Blow Apart. I Would Like To Get A Summer In To Get My Feet Wet.ithank You For Your Time Rob.

I've been using a 28 spline Ford 9 inch for over 4 years now,my big block is probably putting out close to 600 HP,its mostly a street car.We just had it all apart to put a limited slip in a couple of weekends ago and it still looks like new.I have had it to the track a couple of times,no slicks,its a 5 speed tranny,gets used pretty hard at times.I dont think that you will have any problems.
Guy

Let me guess. That guy has another 9" that he will sell you that will handle the bigger power.
That rear will handle the 600hp with no problems.

If it had a Ford Traction Lock in it then I'd say he was pushing it when he said it would handle 400 HP. If you put a spool in it then it will probably be all right with 600HP. If it has a stock Ford case then you wil be at the limit, and you still might break the case where the pilot bearing goes in. A nodular case and Daytona pinion housing would be better.