Welcome to the forum, and congrats on your 850. There are at least a handful of us here who own them, or are otherwise familiar with them. I sold my '68 Spider to my brother last Summer, but I see it and drive it often.
Here's a link to a lowering block that I've heard good things about. If you're handy you could likely build one of these, but a nice finished powder coated product for $69 is hard to turn down. I just "edited" to say that while this was minimized on my laptop, you'd purchased your lowering block. Was it this one?
http://cgi.ebay.com/ebaymotors/FIAT-ABA ... 23086bab5a
Brad's knowledge and advice within his well-known article has helped me with my Twin Cam Fiat quite a bit. Extract as much info as you can from him
I have rebuilt a 30DIC-1 carb for my former '69 Sport Coupe, and it was pretty easy. I used a factory "Major" overhaul kit, and I was done in a half hour. However, I did find after reinstalling the carb that it had most of the same issues it had before. I found that it was the accelerator pedal linkage, the accelerator cable itself, and the armature atop the valve cover that were binding and in need of service.
The best tech tip I can give for the 850 is to replace its factory accelerator cable with a braided brake cable from a tandem bicycle. It sounds weird, but it makes sense; the factory accelerator cable is a solid, non-braided unit that often bends and kinks irreversibly, making it bind within the area between the pedal and the carb. A braided stainless steel cable like one for the tandem bike is long enough to reach, and won't kink or rust. It's worked very well on my brother's 850, and I wish I could take credit for thinking of it!
Other carb options include the more simple single barrel Weber 30ICF, which came standard on many 850s. It might cost you a few hp, but it's a smoother more simple carb than the aptly named DIC. The Dellorto 30FRD is a bolt on replacement, and slight upgrade for the 30ICF. It's said to match the hp of the 30DIC1 with one 30mm barrel.
Another more bitchin option is Cost Mesa R&D's Weber DGV manifold for the 850. It'll allow you to put either the DGV style Weber, or the older/more versatile 36 or 38 Weber DCD. Also offered from the same source is a performance cam that goes very well with this carb/manifold combo.
Check out the following link, and the MANY 850 performance videos this guy has on YouTube. He's extremely nice. He answers his phone, and his email. He races his own 850 regularly.
http://www.youtube.com/watch?v=fbDfT12xNPA
I have a fair amount of 850 parts, hit me up & I might have something you need.
Below is a pic of my former/my brother's '68 850 Spider.
[url=http://www.flickr.com/photos/thech ... .jpg[/img]
project 850-3 by
thechadzone, on Flickr[/url]
Below is a pic of a 903cc motor that was part of the decor of my studio loft apartment for quite a while before being installed in a '68 Sedan.
[url=http://www.flickr.com/photos/thech ... .jpg[/img]
Fiat 850 Art by
thechadzone, on Flickr[/url]
Below is a shot of my former '69 850 Sport Coupe. I regret selling it, but Space Number 69 in the downtown parking garage just wasn't sufficient for the work it needed...
[url=http://www.flickr.com/photos/thech ... .jpg[/img]
Cafe Mam Event & 850 Coupe 035 by
thechadzone, on Flickr[/url]