I'm looking for the front and rear rechromed or new bumpers for a 1970 Oldsmobile 98 convertible? Any suggestions on where to locate them.

 

Look in the classified section here. I thought I saw 70, 98 bumpers a few pages in? At minimum there are several guys online making a living selling Olds parts. Im sure one of them knows where good bumpers are.
Several rechroming services are available as well. The Vette crowd has several high quality replaters that are used for NCRS judging. NorthStar which is now Key Stone in Minneapolis/St Paul did superior work for me. Pauls out of PA is another. These chrome shops also have networks to source cores all over the nation. Get on the Googler...

 

Several guys here, including myself used Ogden Chrome in Ogden Utah. They paid shipping both ways and also arrainged the shipping. Their chrome plating is excellent! More expensive than some and cheaper than some, but excellent work. You can do a search here for them.