"can we use those records to calculate the cost basis?" Yes

"how do we determine which purchase price to use?" FIFO

"with an acquisition date of 11/30/2022"

Is that when he opened the account?  Otherwise, why not use that date instead of FIFO or some other alternative? 

My mistake, that date is apparently when Coinbase transitioned the assets in the account from an older system over to a new one but not the actual date of purchase of those assets.

This is why I spent all the time "decorating" the ceiling over my head at the office. The client could look up for inspiration to select dates & amounts.

Of course you need the client to do the selections and write them down for you. 

@George4Tacks  My clients mostly just have to write down SLY

Mine wrote SALY? Maybe brother & sister?

Saymaz isn't just one word?

 I can go with SALY.... but when it gets to  SALLLLLLLLLLLLY, I draw the line 😉