GTX John the NHRA SS class racer, said he taps his for Holley on both primary and secondary, carefully, in an older thread elsewhere on the net...you can tap coarse to fine using a bottom tap i.e. not as much lead taper in the tap, and perhaps let the small bowls under the jets in place... but...how long will it hold. my experience with rigging like that is...after a few jet changes it'll be stripped out altogether. the threads definitely will be compromised to some degree. there is a brass insert in the bowl with the threads in it, so it's not threading into the black plastic itself. my gut told me years ago, these carbs are cheap enough used in junkyards, scrap piles, sway meets, just buy a number of emission carbs post-'77 model years, and drill those jets in increments beyond the stock size. the jet/spring kits are still on Ebay $50 free shipping for 8 pairs of jet sizes and power piston, accelerator pump springs, which is a deal. thanks for the replies fellas...
