Truck sitting for 30+ years

I am picking up my grandpas '69 C30 here soon. It has been sitting in a barn untouched for over 30 years. I am planning to throw in a JEGS branded 350 w/ Vortec heads, replace the fuel system, throw in a new wiring harness, and a clutch. I will also do fluid changes on the transmission (SM465 I believe) and axle. Is there anything obvious that I will need to replace while I have it torn apart to get it running? I would immediately do the breaking system, but I would like to go to front disks and that seems to be more involved on the C30s.

Thanks