Flight Instructors Manual, RD Campbell.
Excellent material, especially for the long brief part of the FI test
I would consider the choice of aeroplane for the course to bear heavily on the one you are most likely to be teaching on at the end of the course. That said i did my FI course on the C152, now after 200 hrs instructing on that i now teach on the PA28. Only other issue to bear in mind is that there is a Spin test either as part of the main FI test, or this can be done prior to test (with an FIE) If you did the course and test on the C152 then it would save the hassle ofhaving to book 2 aircraft for the test day. (Assuming you refer to the PA28-161, as this cannot be spun, the PA28-140 Cherokee can, IF you can get the CoG in the right place!!) I found the C152 a fun little machine to instruct on, and learn in, even if the cockpit is at best "intimate".
Best of luck either way, its probably the most enjoyable and fulfilling course you are likely to undertake in professional aviation
Hope this helps
ch