Doug's exhaust help '66 Dart

Yes the 273 manifolds will restrict head flow,but if it,s all you have for now,use them.Here,s a link for Summit.http://www.summitracing.com/parts/DOU-D450/Application/?prefilter=1
I hope you have floor shift steering column?There,s also a Dakota manifolds you can use with a bit of massaging to fit.I believe the Dakota year is 91-93.good luck.