"...I was told..."
If you have not already done so, sign up to the Class Racer Info site.
http://www.classracerinfo.com/Selection.aspx
After sign-up click on "Technical Specs for NHRA Classes".
Then enter your engine make & year model. It will show all NHRA legal engines.
When you click on one of those engines it will show most of the legal specs & you can click to another page to see exactly which bodies that engine is legal for, as well as min weights.
I'm no expert here. But I have used that info site to look up lots of possible combinations, especially for Pontiac powered cars. I have found that it is not completely up to date. But, it's probably pretty accurate, for the popular combinations.
Hope this helps. If not, just ignore me.