Here are a few links to give you a heads up on what is needed for the swap and an overview of what needs to be done:
https://honda-tech.com/forums/honda-crx-ef-civic-1988-1991-3/detailed-b-series-into-crx-ef-civic-parts-list-more-2769325/
https://www.crxcommunity.com/threads/b16-swap-guide.173/
https://hondaswap.com/threads/swap-info-for-ef-4th-gen-civic-and-crx.50719/
And here's one with all of the ECU codes:
https://www.phearable.net/information/tech-area/hondaeculist.html
^^^The ECU's on these cars are easy to locate and remove. You can literally just have him remove the ECU and read you the code printed on it to see what you're working with.
One of the links up there also has the engine codes, which you can use to figure out which block the car is running. They're usually printed on the front left side of the block, close to the transmission. USDM vs JDM motors frequently have different block numbers- helpful when you're trying to figure out what's in the car.
I would consider bringing a compression tester.
I've owned and tracked a few golden era Honda's- CRX, EK and DC2. The CRX is the lightest, but I didn't care for the tail-happy short wheelbase on track, nor did I care for the lack of PS around town. It should be noted that I had a 1988 CRX Si (different rear toe mounting point- known to be more tail happy than later years).
If I was building an old Honda track car, and didn't care about things like ABS (hard to find on all of them except the Integra), I would probably start with an EG hatch- very little weight penalty over the CRX, better/revised suspension geometry, more headroom (for a helmet), longer/more stable wheelbase, larger parts availability (essentially the same subframe/suspension as the DC2), available PS, OBD1 (preferred for most tuning options like Hondata S300- not that you can't OBD1 convert an OBD2 car like I did with my DC2 GSR), etc. As a street car, I loved my EK- lots of minor incremental improvements over the EG/DC2, but it's heavier than the EG.