I put a crate E-7 5.0 long block in place of the 302 in a 79. The engine balance is different, so you will need the 87 up balancer and the flywheel/flexplate. I do not remember the crank pulley bolt pattern being a problem, but somewhere along the line it changed. I think a newer clutch assy fit in the SROD bellhousing.
your T-5 will not use the SROD bell housing.
Jrichker already mentioned the cover or electric fuel pump.
With an Edelbrock 302 4bbl intake, the EGR spacer off a truck, a Holley 1850-2 carb, factory headers from an 87 up and dual exhaust, it got 21.5 MPG or better on the highway and was a faster than the 79 302.
Follow this tech note for the best way to wire a fuel pump kill or anti-theft switch...
Note: this only works with full EFI systems. If you are doing carb equipped car, the wire colors and diagram will not work without modification.
Revised 16-Mar-2017 to change wire color and add 91-93 fuel pump wiring diagram.
Note: Use automotive gauge wiring that is rated for 105° C. The wire spool will be marked and the wire may also be marked. The higher temperatures that automotive wiring is exposed to makes this a necessity.
On 86- 91 cars the fuel pump relay is under the driver’s seat, 92 and later cars, the fuel pump relay is under the Mass air duct on the passenger fender well.
Note that the wire colors changed in 1991, so there are two different descriptions.
86-90 model cars:
Cut the Red/Black wire going to the fuel pump relay. Splice a 16 or 18 gauge wire into the wire and connect it to one side of the switch. Connect the other side of the switch to the other end of the red/black wire going to the fuel pump relay. When you are done the switch should be in the middle of the spliced Red/Black wire that goes to and comes from the fuel pump relay. Using the control side of the circuit allows you to use light gauge wire and light duty switches. There is less than 1 amp going through the circuit, so you don’t have to worry about voltage drop across the wiring depriving the fuel pump of electrical power.
91-93 model cars:
Cut the Red wire going to the fuel pump relay. Splice a 16 or 18 gauge wire into the wire and connect it to one side of the switch. Connect the other side of the switch to the other end of the Red wire going to the fuel pump relay. When you are done the switch should be in the middle of the spliced Red wire that goes to and comes from the fuel pump relay. Using the control side of the circuit allows you to use light gauge wire and light duty switches. There is less than 1 amp going through the circuit, so you don’t have to worry about voltage drop across the wiring depriving the fuel pump of electrical power.
The design of this plan doesn't require an expensive or heavy-duty switch. It just needs to be reliable and able to withstand being turned off and on frequently. When you turn it on, it needs to stay on and not turn off . This type of switch is labeled SPST (single pole, single throw). It is a NOT a momentary contact but a constant contact type switch.
Most push button switches and switches that spring the handle back when you let go of it are momentary contact switches. These will not work for a for a fuel pump kill switch.
More information about switches is available at
https://learn.sparkfun.com/tutorials/switch-basics/poles-and-throws-open-and-closed