Cam questions, converting to roller

[eddielugnutz]

I'm converting a non H.O. motor to roller, and to the H.O. firing order, I was going to go with the roller conversion kit in Texasmustang.com, the one that screws in the lifter valley with the the spider pan to hold the roller lifters in place, question is, can i use the stock roller lifters in a older non roller block, or does the block have to be machined for roller lifters?

Second question is about cams, can I use a roller cam with the hydraulic flat tappet cam bearings that are in the motor? are the journal diameters the same, or do I have to get new cam bearings for a roller H.O. motor to fit the roller cam?

If the block needs to be machined for roller lifters and new cam bearings, then i will choose to stay hydraulic, but are there any companies that make hydraulic flat tappet cams with the H.O. firing order, i'm using the fuel injection so I know I need to keep the same firing order, but the older non roller non H.O. 302's have the different firing order,

thank you for your time and advice!