Use a Cooper 'S' damper, or the replacement which Mini Spares sell. It damps out the crankshaft vibrations better. With a 1098 it is very worthwhile to have it dynamically balanced.
A better cam such as a Kent 26, MG Metro or an SW5 will improve it overall and give good torque, which is where the 1098 scores over a 998. As above, lighten the flywheel a bit but not too much.
Fit a higher FDR, I suggest a 3.2:1, and it will drive very well.
You will need an HS4 carb, or twin HS2's. Gas-flow the head a bit and use about 9.75:1 CR.
With a decent exhaust system you should be looking at c.60+ bhp at 5700 with a lot of torque at around 4000 to 5000 rpm and an engine which will pull strongly from around 2500 rpm.
Edited by Cooperman, 24 January 2017 - 05:07 PM.