If AIM-23B / Fakour-90 is comparable weight to AIM-54 Phoenix then maybe it could carry three of those.
Main limitation of F-5E is lack of space for large radar antenna, but removing cannons and its ammunition would allow for more powerful processing components and liquid cooling.
Redesign of F-5E/F by introducing more modern, up to date design elements should be possible with manufacturing tools that there are.
A single turbofan engine of equal or greater output than two J85-GE-21 would take up less space and then with modification of intakes it would allow rear landing gear inside body.
Then wings could be made stronger with some capacity to carry fuel where previously two landing gears in wings would have been thus less need to use fuel drop tanks.
Also with turbofan there would not be need for small air intakes to cool the jet engine and more diverterless supersonic inlet would be viable that are more aerodynamic and lighter.
I doubt that an f5 could carry a single f90/aim54,and even if it could its radar would lack the capability to take advantage of the capabilities and range of either missile.
It would actually make a lot more sense,not to mention be far,far easier,to reengine the mirage f1 fleet with the mig29s rd33 turbofan,rather than attempting to virtually rebuild the f5 to take an rd33.The reengining of the f1 was actually done back in the mid 90s by the south africans and proved to be an excellent conversion,tho ultimately they didnt go ahead with converting the entire fleet on cost grounds.In addition it was also adapted to carry the excellent aa-11/r73 wvr missile,this would also make an ideal conversion for arming the rest of the older western supplied aircraft as currently they only have obsolete sidewinders and sparrows.
Another potential huge force multiplier would be upgrading the mig29 fleet to fulcrum C standard,the dprk has some numbers of fulcrum Cs in its mig29 fleet,so this would in theory allow iran to acquire an example to reverse/reegineer a local equivalent,if combined with a reverse engineered r77,which both the yemenis and venezuelans possess,so no real problems with acquiring samples,this would allow iran to effectively double the size of its bvr capable fighter force.This would obviously be a huge capability upgrade.It would also allow for the possibility of upgrading irans other fighters to be equipped with a modern bvr missile,for instance imagine an f5 with a modern radar and data link capability packing 2 r77s+2 r73s,this would be a nasty combination in anyones book,and theres no reason that you couldnt do the same sort of thing with the f1,f4,f14 etc..
The airforces two biggest problems,imho,seem to be a lack of leadership on the one hand,and with that a lack of [realistic] clear vision and set of goals for the future,and on the other hand just as critically both a lack of technology and a seeming unwillingness,or at least reluctance,to work with those who have that technology,altho one thing that does give one some small hope in that regard was the airforce effectively having no choice but to work with and acquire drones from the irgc affiliated drone producers,plus during the latest military exercises we saw the firing of an old maverick a2g missile that had been upgraded with a modern all weather flir seeker,likely donated from a drone launched munition,instead of the obsolete 1970s era seekers that the iriaf still uses.
In short theres a hell of a lot that the iriaf could do to upgrade both the existing airfleet and its weapons,sadly tho its shows little inclination to do any of these things,and I dont think you can just blame it on a lack of resources,as there were obviously resources when it came to the iriafs 15+ year long failed drone program,not to mention all of the fvcking around with the f5 that the iriaf seems so fixated on for the last 20+ years.
Honestly its pretty sad...