well if the cylinders are all cleaned up ,,,and the motor turns freely ....you can check for lower slop by turning motor over and watching where the pistons top out ...they should pause the same on each cylinder ..if there is slop in one it takes longer ...it that seems good you can actually put heads back on ...i doutb very seriously that the carbs are going to be in good enough shape for it to run ...if the bike has been sitting so long ...
to be honest this bike has shown enough to me that id go all the way checking things out ....i just cant advise a short cut ...now i will say you can wait on staor but what the point the clutch is showing signs of not doing right ....
1200s on the whole are great motors and i advise doing ll possible to check the thing out ....im rather sure there will be carb work to do or switch to single carb ...if diaphams are bad...carbs are rather toast and new will have to found and bought ...or single done ...why chance the motor to carbs that can dump fuel in and backfire or hydrolock and bend a rod ...carbs will have to be cleaned and check for operation and leaking or a known good set put on .....
if i were you id just settle down and stay at it ...your not familiar with these motors like me or others who have time in them and really cant take chances ....to big a gamble in my opinion