so my timing chain started slapping the timing cover on my 390FE, can I leave the engine in the truck and replace it or will I have to pull the engine?

 

Easy to replace "in truck".
Here's a tip, use a timing set from a pre-72 truck. That set's cam timing is "straight up" instead of four degrees retarded like the later sets. The retard was done for emission compliance and cut performance a little.

 

Not what I would call fun but it can be done "in situ"...

 

Yes the motor can be in the truck but depending on the harmonic balancer puller and and installation tool you may have to pull the radiator ..

Installation tool (rent or buy)
http://www.ebay.com/itm/Moroso-61744-Universal-Harmonic-Balancer-Damper-Installation-Tool-w-Adapters-/330958766252?hash=item4d0eae00ac&vxp=mtr

 

my motor is actually a 68 so its already pre 72 and I have a harmonic balancer tool.

 

Cake walk, leave it in the truck. When you go to reinstall timing cover, squirt a little extra RTV where the oil pan, block and timing cover meet.

 

will thank y'all for the confirmation, and If I ever replace the timing chain in my dads 72( has my 73's orginal 360) I will go with the pre72 timing chain.