Hello;
Double check the water jacket hole(s) in the block & heads.
If they macth they will work.
I will tell you this , they did bolt up to my "79" block and the water jacket hole's lined up. and they ported & polished nicelly.
Has for the headers , This should also work since the "8445" heads have the raised exhaust ports. Once again double check against your cast headers. IMO the headers flow better , but wouldn't allow the turbo to spool as quick because of reduced velocity.
According to all the Buick books I have, all 1979 thru 1987 RWD heads are basically the same. There are only minor casting differences. They will fit, but there there is no real advantage to 8445's over what you already have.
The 83/85 headers will fit also. There is something weird about the exhaust manifolds. They were big in 79/80, then small in 81/82, then big again in 83/85. Fred's right, they should flow better than the cast manifolds, especially the 81/82's. But they are very prone to cracking. You might be better off with the bigger 79/80 cast manifolds you aleady have. This should help (a picture's worth a whole buch of words): http://www.flash.net/~rjgeorge/exhaust.htm