113 heads would be great, but remember you are going to lose your EGR since the alum heads do not have the EGR crossovers.
You are also going to need a centerbolt intake since the 113's are off a roller motor.
Pick up quality felpro gasket for a 305 off summit.
Check it out..
http://store.summitracing.com/egnsea...115+4294891421