If you're still going to try the frame out - take the wheels off your bike and at least put it on the frame and check the standover. It sounds like the seatpost is not going to be something you can swap on easily.

I don't know if you have something that you can set in there as a stem (whether it's threaded) and see whether the top tube seems like it'd work for you.

The time I bought a frame & fork only off craigslist - I made sure to bring a seatpost, wheels, and a stem & handlebar that I could stick on the frame quickly & at least tell that I thought it would fit or not. I'd looked at the geometry enough to know that the seattube was the same as what I'd been riding, but the top tube was a bit longer. I also had my old bike with me so I could hold the frames up to each other.

But $150 sounds kinda expensive for that frame & fork. I paid less for the used surly pacer frame & fork that I bought on the for sale section on here.