I have a front header for a 81-83 two door regal. I have a feeling the one you are looking for is like the 78-79-80 regals(more verticle in appearance).
FOR SALE
1983 and earlier front header panel with grill and head light buckets $50
1983 front bumper fillers RH LH $50
1981-87 front RH fender...solid... $35
5W30 synthetic sounds good... if you are in an area that has -30 to -40 there are 0W30 synthetics also made. Most engine wear in normally driven automobiles occurs ar start up due to delayed lubrication, due to too thick an oil.
I have listed a ELECTRONIC TOUCH CLIMATE CONTROL from a 1983 Buick Regal Limited on E-Bay item #230208357847. Just thought I would pass this on to your forum. Never hurts to have a spare of this rare option for a few dollars.