if he started with a "AK flat" (an assumption on my part, based attaching trigger guard & trunnion), then there are holes, mag opening, dimples, top rails, etc already done.
Cold steel solutions sells sheet metal bent in the right shape, but with no holes drilled... they are not a receiver until holes are drilled- just how many holes would require an ATF ruling.
Just out of curiosity, what kind of kit? (not offering to buy, I've got too many projects already ATM)