Yes you need to be very careful about the height of the valve stems above the head. If they are too high the followers will ride the Cam the whole time, preventing the valves from closing and wasting the cam. If they are too low, the follower will run into the spring retainer also resulting in significant damage. Check the Cammer web page and you will see lots of discussion on this topic. Also remember, each of these cammers have different valves so make absolutely sure you get the correct valves for your head. BTW, the valves are getting harder and harder to find. I highly recommend you contact Jerry Woodland and order parts from him (he is very reasonable) plus he knows what he is talking about. If you order from Jerry he includes a very good discussion about the head and what you need to do. If you have a 66 or 67 head, you need to verify the orifice in the head because the earlier heads had too large of a hole resulting in the lashes pumping up too much and wasting the cam. Do not preload the lashers, but rather run the oil pump (in place) with a drill in several locations to set the followers, if you don't you risk wasting the cam. As far as springs I would have you machine shop check them, unless they are broken, they might be OK. For the followers, make sure they are reground (if reusing) or make sure the surface on the new ones is acceptable. There are many horror stories about replacement follower seating surfaces being too course. I just rebuilt my Sprint and ended up regrounding both my cam and followers. Find a reputable machine shop AND assume they have never seen one of these engines because they probably never have. Research the rebuild carefully and bring the machine shop literature about all these specs. If they don't want to listen, get another machine shop. The bottom end is pretty standard, but be very very careful about the head.
Didn't mean to scare you and if you do your research you will be fine. Just completed my rebuild and everything is fine. Lastly, always use a ZDDP additive for your oil, both now and after rebuild.
