I have a chance to buy a 70 Hurst Olds steering box for my 67 442. Does anybody have an idea if this is the same performance/close ratio box like a 79 Monte Carlo SS?

 

Did you mean to type that you have a chance to get a steering box from a 79 HO? Your post was titled 79 HO but you mentioned a 70 HO which don't exist anyway.

Assuming you meant a 79 HO box, then I am fairly certain it will be the same ratio as used in the Monte SS cars. With that said, you may run into a problem as these later steering boxes had a smaller diameter input shaft where the flex joint connects. I know the 83 HO boxes have the smaller input shaft and I'm pretty sure the 79 is the same. If it is the smaller size, your stock flex joint won't fit onto the 79 Box and something tells me the 79 Flex joint won't work with your stock column. I ran into this several years ago when I used all the guts out of an 83 HO box in a 69 Cutlass box and ended up with the smaller input shaft. The parts guy at my local Chevy dealer ended up figuring out that a Corvette flex joint would join the stock 69 column to the smaller input shaft and it worked well. I think it was an 82 Corvette joint but I am not certain.

Sorry I can't be 100% certain on some of the facts but this should give you things to look at before you go too far.