classic auto a/c for a 73 duster will a 72 system fit?

i been looking around for ac for my 73 duster 340, classic only makes an exact fit kit up to 72 . it says it may work for 73 . The install thread on the 72 demon on this forum looks pretty close to 73 duster controls and box. i just dont want to buy the kit and find out nothing fits , Are 72 and 73 dusters pretty close as far as the hvac sytem