Yes, toolbox looks right to me but modified to carry instruments that could only be seen if your head was in the back of your knee!
If you can't get another one then a GRP repair using 'woven roving' sheet on the back and epoxy resin will work well, then fill the front and sand flush.
When you say the oil pump is OK I'm a bit sceptical if it's the original.... I replaced mine ('56 rusty dismantled basket case) with a Morgo pump as part of the rebuild. The BSA-style geared pumps never over impressed me even on the singles and twins but on the SQ4, with double the bottom end to lubricate and the top end coming from the feed side I just didn't want to risk all the time and cost of the rebuild with the original style pump. Might be worth getting the thoughts of others on that topic. Also, I think that the increased flow rate to the top end helps to keep the camshaft lobes better lubricated as the oil drains back down helping to reduce wear.
I still have a box of bits from my rebuild - mainly engine and clutch parts and a few chrome nuts and bolts. Let me know if you have a list of bits that I might be able to help with.
Enjoy your project - I suspect it won't be a quick one!