Boss 429 Cam Tunnel Plug

OI noticed the rear of this Boss 429 block in my shop has a couple of tapped holes near the rear of the cam tunnel.  Was a bolted plug used for these blocks?  I can find nothing on the subject online.

As viewed from the rear of the Boss 429 engine block, the four passages/holes alongside the cam tunnel (two passages on each side) should be 3/8-NPT pipe thread and plugged with a 3/8-NPT pipe plug.

from factory no, but Nascar guys sometimes ran a plate over the rear cam plug. and other racers, be sure to install the correct restrictors in the block if you are building one.