Some good reading here.
http://www.usradiator.com/coresAfter reading this you should be able to make a good decision based on your driving habits and where you live. Radiators are available to be a "drop in fit" so there should be no problems there.
Even though you have a manual transmission you may want to go ahead and get a radiator with the tranny cooler in the bottom in case you ever get lazy or you have knee problems!!
Last radiator I purchased was from Dillon Radiator for my 261 six cylinder. Its actually made by Champion Cooling. $200 delivered to my door and came with a nice radiator cap and fittings.
