5.7 Vortec to 4 speed

[KJSR]

I had this posted in another section but thought it may get more traction here. I know I’m not reinventing the wheel here but I can’t figure out what I’m missing. I have a 1964 C10 with the factory 4 speed. It originally came with a 230 which I replaced with a 5.7 from a 99 Chevy truck. Everything went together fine but I could not get the clutch to work correctly. The disc does not seem to be disengaging. Here is what has been done:

• Engine was built using a stock flywheel and clutch from a 99 Chevy truck. The original throw out bearing from the 64 was used.
• During the initial engine start the clutch issue was discovered. I was unsure of the linkage and the amount of movement the arm required to disengage the 99 clutch properly. I modified the clutch arm to have extended movement at the clutch fork. I am utilizing the inside linkage hole on the fork. The new set up stopped about 4 inches from the floor so I was confident that I was getting full travel. Still wont disengage.
• I read some threads about similar issues. I discovered I had the “short” throw out bearing so I replaced it with the “long” throw out bearing. I also checked the disc to ensure it was installed correctly. Reassembled and re-tested, still wont disengage.
• I have ordered another pressure plate but am not confident that is the issue. I am becoming very proficient at pulling the trans out!

I’m sure someone out there has done this change and had it work. What the heck am I missing? The only other thing I could think of is the throw out bearing snout is too long and pushing into to the disc. With that said there is no smoking gun (signs of wear or other carnage). Any thoughts or experience with my issue? Thanks for your help.