Post a photograph of the engine compartment. From this we can discern whether the original swap was the "JTR method" or the less advantageous non-setback one.
If there's rust in the floorboards, almost certainly there is rust elsewhere, in nontrivial amounts. This may or may not require immediate attention, but it does merit jacking up the car (suitably supporting it!) and a thorough examination. Some rust, while annoying, is only cosmetic.
This particular car evidently has a 5-lug rear conversion. Does it also have a solid rear-axle conversion? Such a conversion remains controversial even to this day... but properly done, it has its own appeal. What is the rear-axle ratio? If the transmission is a TH350, it won't have an overdrive gear, which is annoying on the highway. Lack of overdrive is, in my opinion, the main reason for why a "race car" is unpalatable on the street.... something to consider.
Otherwise the standard routine is to examine and possibly refresh the engine. Do you have specs on the cam? The heads? The compression ratio? Have you done a compression-test? The standard tuning-approach applies, whether it's a Datsun or a Chevelle... lots of literature on that.
BTW congratulations on the purchase! Aesthetically it looks aggressive, without being outright garish. Those fender-flairs nicely split the difference between too-much and not-enough. But I do wonder about the rear axle... the rear wheels aren't particularly wide, yet they protrude considerably outboard. Perhaps the axle is too wide? Could it be narrowed? 4-link or ladder-bar or something else?