Hello, thank you for your inquiry. This material has not been chemically treated.
I'm sorry to say to Alexandria Moulding, that 1.5" is 38.10mm. These parts are not that tall, please inform yourself over your products. This product is 36.00mm tall.
Yes you will have the strength and tolerance to restore your bench. However, the slat dimensions will not likely match your old bench, so that will involve changes, not possible in each case. These pieces have an exact size of 17.46mmx36.0mm.