Re: 5.0 HO EFI to Carb
I did that swap for my 68 about 2 years ago with EFI 5.0 (not H.O but same deal...)
Here is what youll need + few tips:
1. Intake and carb, you can go any where between 500CFM to 650CFM agood idia will be some where in the middle = 600CFM. 500 will be beter for economy
2. you will have to use a 65 oil pan cause the 87-93 were using the duble sump pans and they will not fit cause of the steering parts in your 65.
A good idia if you are alredy opening the pan will be to change the oil pump and have a highe vol' oil pump, it is not expensive (about 70$) and can give your engine a few more years.
3. As james302 wrote, you will have to to change your flex plate to 50 oz.
4. Fuel pump - the 5.0 EFI had a high presure electric fuel pump that will not work with carb, you can buy an electric pump that will work with carbureted engines like the "holley blue" but they are noisy as hall and they will boil your fuel, and if you want to go daily they are not recomended without a bypass and returne line the other option is to change the original timing cover from the EFI engine that had the mechanical fuel pump hole pluged, to a 302 timing cover with the hole for the mechanical fuel pump open (cost about 60$) and install a bullet proof mechanical fuel pump.
You mentioned you are a daily driver, well, me too and the one thing I can tell you I did wrong in the swap is that, I though ..."lets not chnge the timing cover, it is too much work, I'll buy a good electric one, it is more simple"... after starting the engine with the electric pump I wanted to hang myself! the most anoing noise in the world! plus, even if you will buy a quiet pump, they will boill the fuel and themselves and will die fast, I had the holley black that died after 2 moth of daily driving in heavy traffic, I had the holley blue ( yes it was installed by the manual and had good gravity fed) 6 month in the same conditions and it died too, I called holley customer service and quality controll and they shipped me one on there expense, but they said they never ment for a daily "continues use" I have friends using it on the weekend on open rods, that is ok but for the daily, **IT WILL BE WORTH THE EFFORT TO GO WITH MECHNICL** after all that I convert to mechanicle pump and I can't understand how I didnt do it from the begining...
If you will go with mechanicl, it will be a good idia to change a timing chain, you are alredy taking the cover of so you dont have to pay for labor, only 60-80$ more for a good duble roller chaine that will be good for alot of miles...
*you will have to install a pump ECCENTRIC to drive the pump (20$)
5. Pulley - I bought a set of "March performance" serpentine Pulley, I have a friend that succeed to use the 87 pulley on his 65 stang (see the pic, I'll try to get a better one tomorrow ) or you can use the stock 65 so it is realy up to you and your funding...
6. water pump- you need to know 87-93 5.0 had a counter clockwise water pump rotation so if you will use the original 65 pulley, the rotation will be wrong, change the pump or the pulley.
7. The H.O was originally equipping with headers, dont suffocate it with old 289 exhost manifold.
8. The tiny radiator of the 65 will not be sufficient to the H.O, you will have to buy aluminum or abiger radiator (cut the radiator support to fit a biger radiator...
9. Distributor - and for a daily driver you should use a highe energy like the MSD for better starting, beter economy and beter power.