For Mustangs, but can be used on truck engines. Usually $15 used, plus freight.
https://www.ebay.com/itm/Ford-Mustang-5-0L-5-8L-OEM-Distributor-Boot-Water-Seal-E6TZ-12252-A/312793403100?hash=item48d3f08edc:g:sOgAAOSwqHJdmM1g:sc:FedExHomeDelivery!95125!US!-1
On my truck, when I switched to the YF from a 1970 F350, I went with a manual choke kit. It was less than $15 and easy to install. It also acts as a security system since many of today's drivers do not know how to set a choke!
Cory, does the vibration exist at idle speed? If so, remove the v-belts and then see if the vibration goes away. If it does, check H2O pump, alternator, P/S pump, fan, etc.
While searching for NOS parts, this popped up. It is said to be for a van, but this heater core looks like it could be located below or behind a bench seat.
https://www.ebay.com/itm/NOS-OEM-Ford-1983-1989-Econoline-Van-Rear-Heater-Core-1984-1985-1986-1987-1988/141926215203?hash=item210b762e23:g:8boAAOSwll1W1MnX
Can you say torque monster?
Notice the spark leakage on the #1 spark plug.
https://www.bing.com/videos/search?q=Ford+300+miniture+engine+YouTube&view=detail&mid=62E36F141D767CEDBDCE62E36F141D767CEDBDCE&FORM=VIRE