Upgrade for '70 Swinger 340 rear
The ''mostly street'' and ''stock looking'' is the hard part. The rear springs and caltrac type bars would be a nice addition. If your street driving is just local, you could tackle it with small T-bars and some adjustable shocks although it will be a little different handling wise. The bars kinda give away the ''stock look'' though. Back in my day...lol, the biggest bias tire you could fit and some 70/30 rear shocks would hook pretty well, especially on concrete streets, up to about 425hp, but most of these stroker engines are a lot stronger now days.