this is why it is not a good idea to block the by-pass hose. it causes cavitation/pressure at high rpms with thermostat closed.

the heater hose nipple is ok to plug off. just as you have.

you can get the new block off caps at local AP store. when asking = heater core block off caps. most times in the HELP section.

I fill the WP nipple with a good rtv and let cure 24 hrs, then cap it with one of the rubber caps. this way I can always go back to heater lines.

I had a cap blow at 4800 rpm in 2md gear. made a loud bang (cap/water hitting hood?) engine falls on its face and dies. thought I blew engine.

sucked water flooding it and sucking my open filter flat to the base killing it.

yea every couple yrs those need replaced for sure. why I started filling the port on my junk when not used.

I add a spring in lower rad hose to keep them from sucking flat at higher rpm.

check/watch those hose clamps cutting into the rubber as they get old and shrink.

good idea to change both = less than 10$ not counting coolant.

and that is a very nice clean looking engine sir! can of engine brite to wash it down on the list?

do you have the 6 vane or 8 vane pump on there?

6 vane for a/c and 8 vane for non a/c

are those under drive pulleys?

FYI. pump rpm

6 vane on a/c as it uses a smaller/faster pulley to pump x amount at idle.

8 vane on non a/c as it uses a bigger/slower pulley to pump same x amount at idle.

running 8 vane with a/c pulleys can cause pump to cavitate at high rpms for extended run times.

looks like you have a stock non a/c wp pulley size.

I like to run a 8 vane non a/c pulley with a HD max cooling thermo-clutch 7 blade fan on my hot rod.