Can anyone tell me if these are the same, I thought the way the brake plates were held in place was different for a start and I would have thought some dimensions between the two would differ also. Thanks.

Both 240 & 300 Swingarms & frames are completely different. Having said that, the alloy swingarms from later models can be made to fit, but not a job for beginners, as a fair amount of engineering required, i.e  dural parts to machine on lathe, & lots of alloy welding  required. Got a 240 with a 245 alloy swingarm. Have also seen a 300 with a 245 swingarm fitted.

240 / 300 foot peg  lowering / relocation is a good mod.

240 fork angle mod also worth doing, as is beefing up headstock area plating, as its prone to flexing.

300 fork angle is pretty good as standard.  

All good, All sorted. Thanks.