newly built 416 getting warm

just a cooling question here. recently had a 416 stroker motor built from a 340 duster. outside of the obviously larger cubic inch the rest of the package is relitevely mild. it has the original x heads coupled with an elelbrock rpm intake and comp cams 268h hydralic flat tappet and new summitt 750cfm carb. nothing to racey. on the cooling side its all o.e.m with the 22inch 340 radiator (new) with a new thermal fan clutch, stock shroud and 180 thermo all in working order. just started to drive the break in miles and its right at 180 or bellow while under way. when i come to stop and go traffic however it rises quite quickly. later at idle for about 15 minutes it steadily rose to 218 and stabalized. this on a 60' day. obviously radiator time i guess.

so my question is what radiator to get that will fit properly and not look to out of place and where. the engine bay was kept all stock looking and the car is showed. im leaning towards aluminum but need advise. also whats the difference between cross flow and downflow types besides the look? any advantages to either? need to be educated. thanks.