Wow thanks! In my case the swap will pay itself off rather quickly. I have to use 89 octane in my current setup because of compression, so that's 25 cents per gallon more than the ls engine which i could run 87 in. I'd estimate 10k miles per year, is about right. Also in the car's current form I average about 12 mpg. So:
10,000/12=833 gallons@ $3.90 per gallon = $3248 per year.
10,000/20=500 gallons @ $3.65 per gallon = $1825 per year.
That's a $1400 savings per year. So it will just about pay for itself in a years time, but wait there's more
Lets say i get $600 for the engine and trans i have. Well now the swap only costs $900 out of pocket. So if i do this swap this summer then by next summer i would have actually SAVED $500 over not doing the swap. Well what the hell am i waiting for?! Wow I'm excited now