heads replaced have oil in rad no water in oil

Yep, Tom is spot on as usual. Looks like you are going to have to "go back in"...if you DIY that is. If done by a shop, get it back....towed, so they can't accuse you of causing further damage and make them pay the tow bill

Was block thorough cleaned before installing heads? Did you use new head bolts? ( this is a must). Did you torgue the head bolts to proper specs? Did you torgue head bolts in the proper order? If you can answer yes to all of these question I would try backing off on the head bolts and then re torgue them. Make sure you do it in the proper order and also only tighten each one a little at a time. Should take at least three different time thru the torgue sequence to get all the bolts to proper torgue. This could solve your issue. But if not you will need to remove the heads and start from scratch to re install. If you had a shop do all the work then don't sweat any of this do as DavidH25 said and have it towed back to them for them to repair it.

Just a thought. How much oil is in radiator? Are you positive thats is oil? If only a small amount I would try flushing radiator first before doing the above. Might have got something in there during the head change. Not likely but is possible.

theres a UV die that shows up under black light .. maybe add some of that to your oil and see If it shows up in your cooling system