Personally I have not purchased or installed a Holley on my Sprint. I have however looked into it and do know that it has been done many times with success. IIRC looking for an older style (4120?) or some number model is the one that has been used in the past but I would need to look that model number up again. There is no hardware made for the throttle so you'll need to fab something up to make it work.
I have also read where guys have taken other more modern 4 barrel carbs with electric chokes and made them work. Mostly from Cadillacs or Buicks which can be found for less on EvilBay.
In my signature at the bottom here I have a link to the YUKU OHC forum where all of this information is at.
Regarding your QJet I would recommend having Cliff Ruggles rebuild it. He has a long bag log and it may take a year but his work is highly acclaimed.
