Needing advice here...I just got a 1962 Raleigh Gran Sport...and I am having some severe difficulty in getting the seat post back into the frame. I have measured the opening for the seat tube and the seat post itself...from the measurements, it should be a relatively good fit. Interestingly, the seat post is circularly (like a circular stair case) marked almost all the way up the post. This seems to indicate that, when disassembled, the post had to be "twisted" out...almost like screwing it out.
I have tried to measure the seat tube opening for being egg shaped, but it does not appear to be very bad that way.