[66 Stepside C X]

Yesterday I finally got around to installing my HEI, into stock l6 250. Everything fired up.. and set the timing to 10 degrees right were the A mark is... but giving it that much advance seems like it’s setting the idle too high 900-1000rpm were anything I do with the carb with the mixture screw or idle screw are almost having no effect.
I will try bringing down the initial timing just strange that everything I’ve read says 10-14. my vacuum is reading at 19-20. I know there could be a lot of variables i am sure, but before changing to HEI it was at 4° and idle was 650rpm with around 16-17 vacuum. Any suggestions will be helpful. When I did first get it started the timing was at 0, and i slowly turned it up to 10 which raised the idle.

thank you all for any and all the help.