M4RKG

Is It Possible to fit my full system Magnex exhaust from my RST that im strippin onto my XR3i without makin any mods to the exhaust as i hope to fit the engine into it soon but the 3i needs an exhaust asap and dont see the point in buyin one when i have perfectly good magnex lyin in the container??????? anybody able to give me advice on this?? I know that there is a massive difference in the width/diameter in both but surely there must be a way of fittin them (an extension pipe or sumit ) ???? please help ppl