why did the first engine blow up?
if the engine failed due to something about the set up, just swapping parts around isn't going to fix your problem...
Why would you take a Nissan to a Honda shop and expect them to be able to do anything to fix it?
What was wrong with it when you took it to the shop?
What did they fix, and how did they fix it?
If it has a SAFC on it now, it shouldn't be "tuned" why are you needing to get it tuned again? you said the previous owner had it tuned once already...

don't need a standalone unless you're really into messing with settings yourself.... getting a rom tune done at z fever, by martin is as good as it gets in the grand scheme of things. unless you some how managed to figure out something about tuning that martin hasn't been able to figure out through all of his years of doing this, then you're not going to get any better results than he can actually tuning your ecu.
and there is a reason why you see those swaps.
They work. They make power. The parts are there. They are cost effective. They get the results and they last. The people that build things "just" to be "different" just end up with a pile of parts bolted into a chassis, that don't make much power, and a price tag that continues to grow because the reliability just isn't there.
Can you boost a SOHC, yes.
Can you make good power with a SOHC, yes.
will it cost more than pretty much every other swap? Yes.
Is it worth it... not really, especially when you consider how cheap a DOHC engine is, and easy that swap is.
this

i don't think you quite understand the way it works.
the SAFC is more of a general ball park way to tune your set up. See, what it does is intercepts the signal the Mass air flow sensor is sending to the ECU and changes it to something else. Usually, it tells the ECU that there is more air coming into the engine than there really us. The ECU sees the new signal, thinks there is more air, and therefore, dumps more fuel.
You use a wideband o2 sensor as your tuning "tool" This shows you your air to fuel ratio. You adjust the SAFC so that you maintain a safe AFR.
The thing is, the SAFC isn't super exact. Sure, many of the new ones have several different tuning points that are tied to engine speed, but you can't adjust it for every rpm, for every load, for every speed , etc. You just get it close.
In many cases, close is close enough. There are lots of people that are rolling around with just a SAFC tune and that's it. It isn't all that bad as long as you can keep that AFR within a safe range.
The down side is that you usually have to tune it rich so that you stay on the safe side throughout the rpm range, and under all loads. And if anything major changes, like, decreased load at high speed, then the ECU isn't going to properly compensate and you might end up bumping the AFR into the red zone, which could result in engine damage.
So again, they can get you close, but not perfect.
When you take your car in and actually get on the Dyno and get your ECU itself tuned, they are actually changing the programing in the ECU so that it knows exactly the amount of air coming in and exactly the amount of fuel it now needs for the current set up. The fuel maps get changed so that the ECU knows exactly what to do and when to do it. The timing maps can also be adjusted to a much more precise point as well so that your spark timing is exactly where it should be all of the time as well. Getting the ECU tuned is a much more exact process. Usually takes several runs on the dyno and lots of little tweaks. Someone experienced like Martin at Zfever will be able to make most of those adjustments with just a few dyno runs. He's been there, and done that. He'll be able to customize the fuel maps to get exactly what you want. The most power. The most fuel mileage. the best balance of both. He'll be able to squeeze every bit of power out of your engine as safely possible.
Beyond the exactness, and the increased level of engine safety, another big difference between the two methods is the actual power produced.
A SAFC might make 255 whp, and backfire on downshifts, smoke on heavy acceleration, get poor MPG, and have a rough idle.
A real tune could make 275 whp on the same set up, and run as if it was built that way from the factory. Maybe a pop on downshifts, with a smooth idle, smooth power curve and the best possible MPG.

my personal advice, if the engine is currently running and is generally healthy, then I would get my hands on a wideband o2 sensor and gauge. I would use that to monitor my AFRs, and adjust the SAFC as needed.
I wouldn't beat on it too much. I wouldn't expect too much out of it. I would just take it for what it is.
from there, I would make plans to "clean up" my set up. Good injectors, better intercooler, etc etc, And most importantly, getting a real tune.
If I was dead set on keeping the SOHC, then I would make sure that the supporting mods were above par.
Otherwise, I would get my hands on a DOHC engine, have it torn down and properly rebuilt, get that swapped in, boost that and get a real tune.