>> For quite some time now I have been designing a computer that
>> looks like a mainframe from the early 70s

> Paper Tape reader.  Try getting a set of opto-isolators, and
> making your own

This is prefectly reasonable.  You can use one of the
photosensor linear arrays for the sensor too.


> Paper tape punches, could make your own similarly, I'd think;

_Much_ harder to punch holes accurately than the read them.


> Should be able to find a KSR/33 (or ASR/33 or ???) for not too much

You want the ASR/33 teletype.  ASR is Automatic Send/Receive with
a paper tape reader/punch.  KSR was Keyboard Send/Receive with no
paper tape capability.  Doing maintenance and repair on either one
will give you a real appreciation of complex mechanical units.

There are also higher speed paper tape punchs.  Some might be
available as surplus from companies that made tapes for older
CNC tools which used the mylar tapes.

                                                Lee Jones