1966 Barracuda

Hello ALL !!
I have a 1966 Plymouth Barracuda. 273 V8. I am having work done on the vehicle and when they removed the heads (original), they found a crack in each of the heads. BOO !! I had replaced the intake with WEI 8022 Stealth intake manifold and running headers from Doug's Headers: Part # D450. Which all matched and fit perfectly. My question to you all out there is:
Where can I find a set of 273 heads for replacement and to rebuild? Will a set of 318 heads fit with what I am running? Or is there another reasonable option? I'm no gear head so I need layman's terms ... LOL..
Thank you ahead of time for all you help.

Glenn