Without throwing loads of money on the internals then with a good head job and cam then 130ish is about it really.
Its a good figure for a 1800 , 2 litres the way to go really.
I've seen a few peole throw ridiculous amounts at 1800's only to get it on the rollers and be very disapointed.
Displacement beats it every time, blocks are easy and cheap to come by, put new rings and mains in it, get another head, polish it up a little, new valve seals and followers with a cam from kent or piper (268/272) and a four branch, skim the head whack a new gasket in and swap the lot over one weekend,the car will be transformed.
Come and drive mine when I finish it shortly.
I'll show you the sheet with what I spent on it and you'll be surprised with what you can do with a little cash and good knowledge.
A 2litre car with a good head job and standard everything else (including the cam) will easily make 135-140 without breaking sweat, Balance the bottom end and lighten the flywheel and up the fuel delivery and you'll go more.
Dont forget that you lose about 35ish brake through the gearbox when you get yours on the rollers.