In case anyone needs to know this info, I just happen to look in my 1969 Impala A.I.M. and found the part number for the heat riser John Brown posted a pic of and is the same as what I have 2 of... Part #3887024. I Googled the number and found this ebay link...
http://www.ebay.com/itm/NOS-GM-3887024-H...#ht_3282wt_1007
and this link that indicates what that part number was used on...HR024.
http://www.hamiltonmanufacturing.ca/hrv.htm
I hope this helps everyone out. If anyone has a used 3887023 I have the 2 3887024 I'll trade you.