Two into Three will go...

Hello all.
I am wanting to replace the Li s3 150 cc standard engine from an Eibar frame with an Li s2 Italian engine (186 cc already fitted with wide-type silent blocks). When I fit the engine to the frame tighten up the bolt, there is gap between the lug of the engine casing and the engine itself, and a lateral movement of the engine approx. 3-4 mm.
I obviously need to shim the gap to eliminate the engine's movement on the bolt and was wondering how folk have gone about this. Do I fabricate a shim to-fit, or is there something else you can recommend I use, please?
Any help or guidance will be much appreciated, and thanks.
H.
I am wanting to replace the Li s3 150 cc standard engine from an Eibar frame with an Li s2 Italian engine (186 cc already fitted with wide-type silent blocks). When I fit the engine to the frame tighten up the bolt, there is gap between the lug of the engine casing and the engine itself, and a lateral movement of the engine approx. 3-4 mm.
I obviously need to shim the gap to eliminate the engine's movement on the bolt and was wondering how folk have gone about this. Do I fabricate a shim to-fit, or is there something else you can recommend I use, please?
Any help or guidance will be much appreciated, and thanks.
H.