Will the bolt assembly of a reminton mod. 742 3006 work in a mod. 742 308 cal. will they interchange?

What is your question?

https://www.sportsmansguide.com/product/index/savage-10-fcp-sr-308-winchester-10-round-magazine?a=1924722

This is also avaiable from Walmart at last check.

The rifle is from after 1952 but the serial number is from 1938
As the 308 round only became available after 1952 but without the full number to age it value will be hard to tie down

Is the bolt lost or or broken?

It may be difficult to find a standalone bolt, but .243 is based on the .308 cartridge so any caliber that is based on the .308 will work: .243, .260, .308, 7mm-08, etc, etc, etc.

If the bolt is simply damaged, it may be easier to repair it than to replace it.

Check Numerich. They're currently listed as sold out on their site, but it might be worth making a phone call and checking with them to see if they have any or can get one.

Also, check gunbroker listings regularly. It's unlikely that you'll find just a bolt, but you might be able to locate a good 'donor gun', and then part out the rest of it.

You'll still want to be sure and have a competent gunsmith check headspacing after you replace the bolt, just to ensure that they are a safe combination. Any time you replace a bolt you need to check headspace. If the headspacing isn't correct, a good smith will be able to set it correctly with a small amount of machine work.

It's a Swiss Schmidt-Rubin.

The ring (instead of a cocking knob) at the rear of the bolt, the bolt handle, and the magazine give it away.

It's a straight-pull bolt (the bolt pulls straight back, instead of the more common turn-bolt, that requires the bolt to be rotated before pulling back).

Go to the Remington Firearms Co. website. At the top of the page, click on Support, then click on Owners manuals. They list the Remington model 12 as one of the one's they have. It will be a photo copy of the original owners manual.

go to gunbroker.com or e-bay . you can also try gunpartscompany.com