22R and 22REC heads are not interchangeable.
The blocks and heads are specific to those models.

A 22R head is thicker because the dome of the piston actually fits up
into the head.
22REC heads are thinner because the piston is flat on top.

If both engines are carbureted

If your engine is a 22R then you will have to find a 22R head or get
your existing head rebuilt.

Used heads go for around $75 to $100 from a junkyard, and a simple
cleaning and pressure test should cost under $100 at an automotive
machine shop.

Many of the other parts are interchangeable between the engines, such
as; rocker arms, cam, and the main crank.

Because the blocks are different, the timing chain cover, water pump and
oil pump are also different, and require the correct gaskets.

Make sure to specify the year of the engine to the parts store.
'84 and earlier is 22R, '85 and later is usually 22REC, but there were a
few '85's with 22R's.

BTW 22R, 22RE, and 22REC can be a bit confusing if you look in a factory
manual.

Toyota called all the engines from '79 to '95 22R's if they were
carbureted, and 22RE if they were fuel injected.

The 22REC can be fuel injected or carbureted.
Also the 22RTEC, is the turbo engine and has a different head and block
from all the others because of extra oil and coolant passages for the
turbo.

I think at last count I have six or seven 22R and 22REC heads in my shop.
Some are damaged, and some haven't been cleaned up yet.

I keep spares around now just in case.

I have 2 toy trucks I keep running, so I stock lots of spare parts.

Craigslist has been an excellent source of parts for me here in Seattle.

Sometimes it is cheaper to get a whole junker truck just for the parts
you can strip off, and then resell the body.