Need some advice 318 POLY vs 318 LA

I have the opportunity to buy a '66 Belvedere 4dr. (I know it's a B Body but I always get good advice from my A Body friends). It has the 318 Poly engine. I believe that they were built with forged cranks.. Is this true? I don't really plan to modify that engine. Are parts available (water pump, distributors etc) for this motor or is it gonna be a challenge finding stuff? Also are they much heavier than the 318 LA? Any other info or comments regarding the benefits or problems of these polys would be appreciated.