Is it ok to substitute ipa with everclear?, specifically thinking about a BLAB

As long as it is anhydrous, yes, it is ok.

everclear is only 95% ethanol.
there are many routes to get it up over 99%. a notable one here is lime (calcium hydroxide) since it is easily obtained. i have not used this method, but i suppose one would pour lime into a jar of everclear, and shake it, let it settle, then decant. do this a few times, and filter. expect to lose some alcohol.

i have successfully used zeolites type 3a to go from 90 to 99+%.

Would this procedure also work for IPA. I have 91% IPA, or would 91% IPA work?

not sure if lime would dry 91% ipa.-probably. if u want to dehydrate ipa, then use magnesium or sodium sulfate salt. it is easy to find and use in this way.
the OP was asking about using everclear in a BLAB tek (which precipitates spice from d-limonene with IPA). for this tek, i believe the fumaric saturated ipa or ethanol should be dry (99%+).

and to add to my previous post:

lime is one of the oldest routes to dry ethanol. lime meaning calcium oxide. the water in the ethanol reacts to form calcium hydroxide apparently.

it is also probably best to leave the 95% ethanol soak in a sealed container with calcium oxide overnight unless u have an alcoholmeter accurate in higher proofs.