There is no way around it but a dyno tune for proper tuning. Once you use a dyno you realize that any other means is just guess work. Only exception is fueling which can be done accurately on road as well as dyno, spark though is only possible to get accurate via the dyno.
As for your conversion, it really depends on the exhaust which can make a big change to advance and fueling requirements if say going from stock to tuned headers. If not than stock memcal will be good enough or a known tickled up one.
Only other thing to say about it is... if someone has tuned a similar setup on a dyno before they know where the limits are with timing/torque/power and then can be done with fuel on road with a wideband log!
Road or dyno tune would be the better way to go about it.
Have had a couple mail-order tunes for stock engines no issues except current v8 conversion with unknown engine & small cam...chasing my tale with weird issues.
both options have a very valid place, theres some things you just cant do unless your on a dyno and there are some situations you just cant simulate on the dyno and need rear world driving to do...
No matter what the question is, the answer is always more horsepower!
I've tuned a dirt track car in a paddock with wideband then a fed years later put it on the dyno for a tweak gained 100nm right through the rev range.ive had na 304s on there that I've street tuned and gained 5kw and hold the power a little bit further but no huge difference but it's faster easier and safer and for high power car like the vb v6 turbo that get no traction its a dream 2 degrees timing and a little trim on the fuel can pick up 50hp that you can't even tell on the street struggling for grip lol
If Its Got Gas Or Ass Count Me In.if it cant be fixed with a hammer you have an electrical problem
And on my car I found I had to pull a ton of timing out, made the exact same power but way safer tune. On the road I could not tell a thing going on with the spark map, there was no change in the feel. Dyno told me I was way over advancing the timing.
