Yo Jack,
Welcome!
California emissions and any changes to our Broncos seem to be a crap shoot, somask around local speed shops.
One tip is to run the plug wires to match the cam's firing order.
Here are the 1990 Bronco Pre-Delivery Shop & Electrical & Vacuum Troubleshooting Manuals (EVTM), Partial by member Kingfish999 in Google Drive @
https://drive.google.com/drive/mobile/folders/0BzRTW4yeT2u4UkhzR0ZydDd3MzA?usp=sharing&tid=0BzRTW4yeT2u4NXB6NW5neFRoZGc
Find page # of item desired in contents, then flip screen down like spinning a thumbwheel, then stopping periodically to see what page you are on.
Suggest you download for faster scrolling and to use the table of contents index.
1990 Ford Bronco Brochure, partial by El Kabong @
1990 Ford Bronco Brochure pictures, videos, and sounds | SuperMotors.net
Free registration for some wiring diagrams (86 through 96) and Technical Service Bulletins, (80 through 96), same as by Ford @
BBB Industries- Premium Alternators, Starters, Power Steering Products and Turbochargers | TSB and Wiring Diagrams Database End-User License Agreement
For the roller 5.0 consider Mass Air Flow (MAF):
Speed Density to Mass Air Conversion & Parts List with Cost for Bronco, F 150 & Mustang Source: by C. Asaravala @
Ford F-150 Mass Air Conversion - FordMuscle
Speed Density to Mass Air Conversion & Parts List with Cost for F150, Bronco, Mustang, Part 2 via web.archive @
Ford F-150 Mass Air Conversion - FordMuscle
Speed Density to Mass Air Conversion & Parts List with Cost for F150, Bronco, Mustang; part 3
Source: by C. Asaravala at fordmuscle.com via web.archive @
Speed Density to Mass Air Conversion. F150, Bronco, Mustang.
and as C. Asaravala at fordmuscle.com via web.archive.org wrote;
"...There are several ways to go about making the conversion on 1987 to 1993 pickups or Broncos. However the preferred method largely depends on the type of transmission you have. If your truck has the E4OD automatic transmission (typical on the 351 and 460 equipped trucks and 93-95 Lightnings) then you have to consider that this transmission is controlled via the engine's computer. The most common mass air conversion calls for using the 88-93 Mustang computer, which does not have E4OD control. The options in this situation are to use a 1995 or 1996 F-150 or Bronco computer, as by that year the trucks were mass-air and all running E4OD's.
Other E4OD owners have creatively performed the mass-air conversion using the Mustang computer to control all the engine functions, while retaining the stock speed density computer to handle the electronic transmission. Finally, many have taken the more drastic approach and replaced the E40D with an AOD, C6 or manual gear box. Either way, if you have an E4OD equipped F-150, Bronco or Lightning and want mass air, you have some research to do.
MAF Upgrade by SeattleFSB @
http://www.fullsizebronco.com/forum/7-1980-96-bronco-tech/164963-maf-upgrade-lessons-learned-thread.html
...
91 Bronco 5.0 gets a roller style cam & roller lifters by Bruce S @ FOUR WHEELER NETWORK
