Let's see...

1. - I imagine there probably is, but I'm not 100% sure...

2. - Yes... Stock output is 65-85amps - too weak IMO. Take a look on Ebay - you can usually find the 110-130amp units for the 5vzfe. Also, if you want the max power & don't mind spending some coin you can take a look at NWOR's 160amp unit (I'm happy with it, but it was close to $500) or PowerMaster (alternators associated with their welding equipment).

3. - Optima... I run the blue top deep cycle (just 'cause I wanted the extra set of posts). Only thing is I had to make some slack in the positive lead (cut a couple zip ties to loosen it up) & bend the top support bracket down about .5" (the Optima's are shorter than OEM). Nothing to it. I can take a couple pics for you if want - PM me an email addy...

Good idea for the inverter, but is 400w enough? What do you plan on running on it? May want to think about returning it & getting a bigger one if you want to run a blender/hairdryer size item. <img src="/forums/images/graemlins/cheers.gif" alt="" />