Nubie w/ head and tranny swap questions

[crzyflyboy]

Hey all!

Well, first off, I have a 91 Civic DX Hatch automatic that I busted up the front end on. Drivetrain is undamaged and only has 125K original miles. Long story short..instead of fixing it, I found another car. The new car is a 90 Civic DX?? with a 4spd manual tranny. Engine cranks but won't start. I checked it yesterday and have no compression on #1 cylinder. I drive around 4K miles/month, so MPG is a priority. I'm pretty mechanically inclined, though don't know much about Honda swaps. Seems that many of the members here have Hondas, so I thought I'd give it a whirl.
My intentions were to make the 90 Civic a "HF" model. I planned to get the 5spd HF tranny, head, intake and ECU and swap it all out. After reading posts, I read a bunch of opinions on the matter, and am at a standstill as to it being worth the effort. The 91 DX was getting an average of 30-35mpg, though I would like to get at least 40+ without any major modifications or headache. I'll be pulling the engine regardless, so engine/tranny, ecu swaps are encouraged. I'd appreciate all of your comments and opinions. I'm happy to be onboard!