Run an ENGLE K65 in your bus motor. It is a great bottom end cam and very smooth, drivable. You will love it. A friend of mine ran it in his 2 liter motor with dual 42 DCNFs and could cruise at 80mph on the freeway cross country. Very impressive performance. Don't let the specs fool you. The small overlap on the cam shuts the valve sooner giving it better bottom end performance.
That it should be really gentle on valvetrain too. It has quite slow ramps.
FK-65 280º 236º .342" 8.69 108º
Compared to the W-110 it has four degrees fewer advertised duration and nine degrees fewer advertised duration.
W-110 284º 247º .392" 9.96 108º
In fact at .050" it's basically a W-100 but it has a tiny bit more seat time.
W-100 276º 236º 0.383" 9.73 108º
I don't have intake-valve closing specs on that particular cam but the .050" specs are so close to the W-100 that we can use that cam's specs to determine the correct CR. The W-100 closes the intake valve at 42 degrees ATDC (stock cams close it at about 35 degrees ATDC).
I know for a fact that 87-octane fuel will support 8.1:1 with a stock cam if you get the deck tight (I'm at .055" which isn't exactly tight but it works). That cam/compression combo yields a 7.55:1 effective CR. So we can use that as a reference point.
Your engine isn't exactly identical to a 1600 and we have to account for that. The reduced rod ratio that results from an 82 crank with stock rods will increase the effective CR. So to get a 7.6:1 effective CR you'd have to reduce the static CR to a scanty 8.26:1. Of course that's to run 87-octane fuel so I'd crank in at least another .5 or .75 point static CR and run 89- or 92-octane fuel (I'm going by R+M/2 US specs so you'll have to convert those numbers to the RON figures the rest of the world uses).
Bumping the static CR to say 8.8:1 would give you 8.05:1 effective CR in a 2110 with a cam that closes the intake at 42 degrees ATDC. 89-octane fuel should handle that.
The rub is building a 2110 with only 8.8:1. You have to take some drastic measures to get the CR that low. For example, to get that with ~52cc chambers would take .100 deck height. Deck heights that loose tend to diminish detonation resistance and increase head temps.
There's another alternative. You can use a cam that closes the intake valves later to diminish the compression. The W-110 for example closes the intakes at 51.5 degrees ATDC. So in a 2110 you could raise the effective CR to 9.23:1 to achieve 8.05:1 effective CR. You could reduce the deck to around .08". That's not great but it's better. But since you'd have to build the engine to operate at a faster speed range you could increase the chamber volume by unshrouding the valves.
So say you opened the chambers to 52cc (possible by opening for 90.5s and big valves). You could decrease the deck to .055" and take advantage of a little bit of quench to increase detonation resistance. That would give you 9.24:1 static CR and 8.07:1 effective CR. I'm pretty confident that 89-octane fuel would support that if you got the jetting right. At a last resort you could run 92-octane fuel.
But these are all things that you should discuss with cam grinders and head builders. It's a bit of work but it's totally worth it.