Water pump bolt replacement?

Putting on new water pump and when torquing (30 ft/lbs) the upper DS long bolt that goes into the coolant chamber, it stripped the tip of the threads on the bolt. I had put on a washer on the head of the bolt because it was getting caught up on the bracket to adjust the power steering pump belt tension. The washer gave it just a little less grab and it failed. I need to replace the bolt and want to use one a little longer (1/4”) to keep the washer. Can I pick up a zinc plated 3/8” bolt from a local farm store or not? I’ve seen the replacement Dorman kits are either zinc plated or coated in black oxide. I just want to make sure it doesn’t rust in there. If yes, grade 5? Yes I know I need to RTV the bolt threads. Thanks for any help.

You could do that to get by , you can also get engine bolt kits from several resto companies and I believe they all sell atk brand or similar. Year one would have them I’m sure, if you not worried about correct head stamping, grade and coating anything close would work it’s all up to you and how fast you want it.

I ended up using a 5” stainless steel 3/8-16 bolt and it seems fine. The OE was 4.5” without the washer. Fingers crossed.

Dose the stainless one's have the same grade hardness. I like stainless but we have seen that the thread's will stretch.

You're good. The stainless is probably a 100% improvement over what was in there.

McMaster-Carr
Go to the hex bolts/screws section. Look for the 'Extreme Strength' flange head bolts. They don't show the brand names of the stuff they sell but any time I've bought those they were ARP, in stainless or black oxide.