I've never seen a chain break. I've seen guides and sprockets go but never a chain. SOMETHING has to be binding, seizing, etc. Chains just don't break... especially new ones.

 

Timing Chains rarely break, but if it does it has a ton of mileage on it.
There has to be something else wrong contributing to it.

He has a 1994 20R 4W drive pickup

I hope you have that wrong, the 20R was replaced by the 22R in 1981, and later by the 22RE.
If he's forcing a 20R chain onto a 22RE, maybe that's the answer.

 

Was the kit really cheap? Might have been a subpar product (assuming he is installing the correct chain for his engine).

 

are the gears being put on correctly? they are reversible on the crank and cam. that would result in the chain not being in line with them.

 

just a thought
If he has removed the oil pump during these changes it is important to put
the three bolts that attach the oil pump to the timing cover in the correct hole.
the hole in the top @ 12:00 pos. goes completely through the cover and the bolts are different in lenght and installing the wrong one in the wrong position could allow it to
protrude through cover thus itnerfering with the timing chain