Frame or chassis options for A bodies
For a stock style suspension the most often recommended chassis stiffening is sub frame connectors, inner fender braces, lower radiator support brace and a stiffened K frame.
You can pick up these pieces from
hotchkis
http://www.hotchkis.net/search-by-vehicle-results/?mk=40&yr=1967&md=300&sm=39&category1&show=all#10
us car tool
http://store.uscartool.com/Mopar-A-body_c_38.html
firm feel
http://firmfeel.com/a_body_mopar_parts.html
or talk to peter (GMachineDartGT) at bergman auto craft he'll get you set up
http://bergmanautocraft.com/
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