Going from a 170 to a 180 is a pretty big transition. Not rocket science, though. In my opinion, the converted 175 flies a lot more like the 180 than the 170 does, so you may be at least part way there.
You really, really need to find a competent instructor in the 180, however, and get a thorough check out in it. The 180 is heavier....and it demands that you stay on top of it landing or taking off, a bit more so than the 170 or 175. Again, not huge differences, but I've always told folks that you CAN allow a 170 to wander a bit, and get away with it. But, if a 180 or especially a 185 starts to swerve, you'd best recognize it and FIX it right now.
You're going to have a lot more engine management to take care of. Lots of HP and constant speed prop. Again, not huge stuff, but get some power charts if there aren't any with the plane's paperwork, study them, and experiment with different cruise power settings. And, in the process, learn to use the engine and prop.
As to radios: If those old King radios are still working fine, first thing I'd do is install a GOOD engine instrument, as in a JPI 900 or 930 or an EI version. The biggest bonus there initially is going to be a fuel flow computer, which comes with any of those units. With the relatively small tanks on that early 180, life will be a LOT easier with a fuel computer.
There are lots of good radios out there these days. But, again, I'd fly it for a while with the existing stuff, see what else is going to pop up in this new to you machine, and after a year or if a radio checks out, THEN decide what radios you want and need. By then you'll have a better idea of what will best suit your needs.
Should be a fun airplane. One of the first things I'd look at is gear alignment. If the plane seems to have a mind of it's own on the runway, maybe get the gear put on grease plates and aligned.
Most of all, enjoy it. Again, unless you have radios that don't work, I'd put off that stuff for a little while. Almost every plane I've ever met came with a few things that I thought needed to be addressed. So, deal with the priorities first.
Interiors: Selkirk makes good stuff. I'd go with an Airglas extended baggage, though, lighter.
Enjoy it, get a good checkout and have fun!
MTV