I have a 68/69 1500 type1 swing axel transmission for my street buggy project and I need a new motor as the old one has seen better days. I would like to get a good second hand motor and I am wondering whether a later model type 1 dual port 1600 motor will bolt staight on. I am also considering a new mexican long block if I can scape together enough dollars.

Any advice as to which motor to look out for would be much appreciated.

yep straight in and if you are buying a second motor it would be a good chance to build a nice 1641 0r 1776 using your own stuff
there are a lot of builders around and someone will steer you in the right direction