'Silentbloc' is the joint between the center link (aka center tie rod) and Pitman arm (aka drop
arm), plus the joint between the center link and the idler arm (aka idler
lever).  They consist of a center steel pin and an outer steel sleeve, with
*rubber* bonded between the two steel parts.  - Often fails in a few years.

Alternatives:

Steel pin in brass bushing:  about $100/pair
http://www.britishframeandengine.com/parts1.html

Joe Alexander (aka ARE) makes them using Delrin instead of brass.
I've heard you can order these direct from TRF now, but don't seem
to find them on their website.  I got mine directly from Joe by emailing
him at N197TR4@cs.com

>That would be TRF Part Number HP-301.

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I would suggest a gasket.  Since your box has obviously been apart before,
IMO you should also set the endplay with a dial indicator.  Add shims until
you can measure some endfloat, then subtract shims equal to the measured
value (or .001"-.002" more).

Enco usually has a dial indicator set on sale for under $20.  Although it's
a rarely used tool, IMO it's worth buying even if all you ever do is rebuild
the steering box with it.  The part number changes with every sale though,
so go to
http://www.use-enco.com
and click on "Hot Deals", then "Measuring Tools", then "Enco Dial Indicators
& Point Sets".  Look for the set that includes a magnetic base.  The point
set isn't necessary for most jobs (including the steering box), but for $2 I
bought one anyway.  So this month's part number is RN625-1340.

http://www.use-enco.com/CGI/INSRIT?PMAKA=RN625-1340

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If converting to rack and pinion, use this swivel contact mechanism
to use original control head signals and horn:

https://www.scparts.co.uk/sc_en/british-cars/triumph/triumph-tr2-to-tr4a-1953-1967/competition-parts-and-accessories/steering/contact-mechanism-126688.html