Pintos are easy to thaw out, just take the fan belt off and run it for 3 mins then stand for 20 and hey presto, unfrozen engine
I have in the past used a camping stove under the sump to defreeze a Di
I allways have a 50/50 mix all year round but when i had a leak i did freeze me old recovery , twice

in the same week
Or i use that glycol stuff royal mail use neat, drained a written off LDV in a breakers for it last year (then got the frikken van written off a week later)

but you have to flush the system really well to use that stuff propperly but its really stops the internal rust, had a few ex PO LDV in bits and inside the blocks they are MINT! even after 100K +