[V50_M66]

Welcome, and congrats!
These engines aren't worth pinning as stated. These engines will run with a slipped liner for tens of thousands of miles. Not worth the risk IMO. Save the money for an LS swap.
Also, if you haven't already, invest in all new cooling system parts (EVERY hose in it, and a new 180 t-stat) . At this age, they will fail, and loss of coolant will strand you (ask me how I know). Hell, the 180 thermostat may keep the liners from moving around, since that usually only happens when it gets hot.

 

[V50_M66]

Already got that done, replaced most messed up hoses and the t stat. Also I’m doing all the work, so pinning the liners is costing only as much as the pins. And yeah it runs pretty good with it slipping but I’m kinda tired of it sounding like a train.

Get some noise cancelling headphones LOL
From what I've read, you're more likely to blow up the engine trying to pin it than you are to keep the liners from moving.

 

[V50_M66]

Thanks for the concern guys but I think we’ve got it, we’re planning on being one of the pinned ones that run. We already rebuilt/replaced just about everything up top except the heads (Crankshaft, timing chain, gears, lifters, rockers, and the rocker shafts). I’m not quite ready to give up on making this thing run the best it can!

Personally, I wouldn't risk all the work you've already done, and would highly suggest considering otherwise. However, it is your truck, and if you're comfortable with that risk, that's your call. If you do go forward with pinning the liners, be sure to update us on here - I'm sure many of us are nevertheless curious to the process and outcome of the work.
Good luck!

 

[V50_M66]

20W oil is not an option for the Thor engine... at least not recommended by the builder according to the WsM:
Engine oil - V8 - low compression engine
Use a 10W/40 oil meeting specification ACEA: A2,
and having a viscosity band recommended for the
temperature range of your locality.
Engine oil - V8 - high compression engine
Use a 5W/30 oil meeting specification ACEA: A1,
(API SJ or ILSAC GF2 for USA).
NOTE: ACEA: A2 can be used.
View attachment 95372

This. 10W-40 (or in cases of worn engines, 15W-40 Shell Rotella) is the proper oil.