I looked at steel, pole, stick framed different LxW dimensions and wall heights. For me land space was not an issue, just trying to get the most for my $. I ended up with stick framed 36x72x16 with 14' wide lean to's down each side and 2 12x14' doors in one gable end. Trusses for 40'W were significantly more cost than 36'W and 16' high wasn't much more than 14', 72'L wasn't much more than 60'. I will build a 16'x36' workshop inside the back that will be conditioned year round and have a loft above for storage to clear out floor space in the rest of the building.
The lean to is a good call on your part, the cost is minimal vs. the bonus of covered storage outside the shop.
What are your plans for lighting? I lucked out and found a bunch of surplus 400W Metal Halide fixtures on Craigslist for a great deal. They're not the latest and greatest but I saved a ton of $$ and it's BRIGHT
Keep us posted on your progress!