Alan,
T-80 chassie is needed for that howitzer. Don't think it'll be a good idea to create new T-80 model after the Revell one (well, the Revell kit has many mistakes, but not more than ESCI T-62 .... and our T-62 is not on much demand on the model market)... Believe You understood what I meant....
As for 2S3 and 2S7: 2S3 is more preferable chassie, because of many vehicles on a same chassie. This one is interesting project, but not for the next year... Sorry....
Sincerely Alexey.
http://www.acemodel.com.ua