WHY do you want to use them???
I am one of those 'circle track guys' who, like many others, use to use them thinking this was a good thing. But now almost all circle track engine builders are getting away from them. The initial idea was that a roller cam motor didn't need as much oil upstairs, so keep it down on the crank.
Then the flat tappet guys followed suit but soon were finding top end failures a lot from overheated springs and valves due to the lack of cooling oil to them. Of course most dirt circle classes don't allow roller cams anyways, so the monkey see - monkey do tricks were killing our motors. Now the roller guys are questioning their use too.
70 lbs at cold idle is a LOT. You don't need or want anything more than that all the time or you will find other problems develop, such as washed out bearings, etc. My current monster engine has 70 at cold startup and 50 at hot shutdown after a 20 lap hot feature, running 20-50 Joe Gibbs Synthetic Racing Oil, and the engine builder says that is well withing normal specs with nothing to worry about.
I have about four sets of SBC restrictors and I will give you a set free if you promise to not tell anyone where you got them, and promise to not sue me when your engine fails due to lack of proper oil cooling upstairs. PM me your address and I will send them to you if you really want... as I will never use any of them ever again...