its a 91 auto tune port 305, I have hedman long tubes, and a cai. Everything else is stock, rear end howls, so I'm rebuilding it, either 3.42's or 3.73's. I hear tune port run out of gear fast with 3.73's but I'm just looking for an around town car weekend driver, so I'm unsure about gears. I'm thinking the zz4 cam, will this be ok with a stock 305? Also, I'm running a 100 shot of juice, is the zz4 ok for nitrous on a stock 305? Any suggestions.

 

Is this an auto trans car? If so, I think you want at least a 2600 stall converter to get the most out of that ZZ4 cam. Same for the gears, the 305 will need all the help it can get, so go with the 3.73's for around town/weekend driver.
The cam will work great with the nitrous.
If it were mine and I was staying with the TPI setup, I'd put a stock LT1 cam in there and keep the lower rpm's as strong as possible. Stock LT1 cams work great all way up to a 150 shot.

 

youll either have to machine your heads or buy special retainers or locks with new springs that can handle the lift of the zz4 cam. better off getting 3.42's IMO.

 

I have a 3.73 in my 305 car.

GO WITH THEM! I love it and I drive around town no problem.
1st gears short. And you have to watch it when you downshift. Other then that..........its awsome!

 

with that cam you will need new springs. some comp pn#981 springs will work fine. you will also need some new retainers. "I" would do this for either of the cams stated (LT1 or zz4).
as for gears... if its for racing go with 373. but if gas milage is ANY concern to you (or if you get the LT1 cam) get the 3.42s, both will do the job.