The MP templates are for bowl porting primarily. I'm hoping this wordy response helps to understand the whys in regard to me advising you to have good head work done.
The thought behind a good seat angle is because for the best flow regardless of lift you need a clean edge on the intake valve seat between the approach, the seat angle itself, and the transition to the throat area of the port. Think of two pieces of pvc pipe that join with an elbow. Air basically behaves like a fluid when it's flowing: it doesn't turn well. Especially around sharp edges. You want to smooth any transitions that result from a change in direction. When V8 OHV engines were new, valve jobs were one angle. The seat. The point the valve and head touched and sealed. It's easy to mass produce, very forgiving in terms of ability to seal even when worn miserably, and easily duplicated as a repair procedure. This was what a valve job was in the 50s,60, and 70s. The grinding of the seat was done using a tapered pilot, and stones that grind away the material. The issues with a stone seat are these: the guides condition is irrelevant because a tapered pilot wedges itself into the guide. By its very nature this does not, and cannot locate the precise center of the guide like the valve once installed. So those pilots could be off center, causing the seat to be ground off center in relation to the valve, and the seat to be basically junk in terms of high performance. Runable, but not good. The pilot was the locator of the stones that grind the angle into the seat. One stone, one angle. There is a certain tolerance between the stone and the pilot... Wear on the pilot or stone cases the stone to be able to wander and chatter leaving a rougher, harder to seal on seat surface. Add to this the inability of some to feel and do a good stone valve job, and the associated wear on the stones as they grind... It all adds up to poorer tolerances, more out of round seats, and lost performance. In this case, "performance" means power, economy, and longevity. Not just hp. So you can grind a bad seat on a good guide (or a poor one), and the engine will run. But it won't last well, may have rocker geometry issues, and will make a fraction of the power it could make if the work was done more precisely. This is not to say stone valve jobs suck. Most do, a few don't. But the ones that don't take a ton of skill, experience, and attention during the work to be good. I've done a few stone ones and I am not that talented...lol. That's why I bought my TCM-25.
Modern engines have much tighter tolerances for machining on the heads (among other parts). 4-valve heads, rpms into the 8K range, serious boost, and emissions/reliability demanded that. If my Neon's 2.0L DOHC was made into a V8, with no other changes, the 4.0L would make 340hp. There's reasons for that. Some of them are much more precise machining. Also explains how Stock Eliminator racers can get 1.5hp per cubic and more inch from basically stock parts. So how do we get the tighter tolerances and better stuff? Technological improvement.
The multi-angle seats were initially done using stones too. But the slop in the pilot/drive/stone system kept the quality only so good. On modern heads it would not fit the bill at all. So, now we have cutters. One cutter with 3 or 5 or 7 angles, all on one holder, that has an integral straight pilot that fits the guide just as the valve does. Because its cut, not ground, there are less jagged edges between the angles of the approach, seat, and throat to hurt low lift flow, 100% concentric cuts, and we can accomplish the basic porting actions of bowl hogging and unshrouding the chamber side just by doing the valve job. A 5 angle is a 3 angle with porting...lol. One angle is added for the throat (which is what the MP templates were for the most part) and another is added for the chamber entry to remove the shrouding effects that cutting a seat deeper leaves. Not to mention the accuracy of seat depth vs valve length (critical on Mopar shaft systems), the process of cutting down guides, replacing guides, cutting and replacing valve seats, or cutting spring seats can all be done on the same machining center which cuts costs and time.
Now obviously if you have a grinder and stones in the garage and this is free work, I'm going to assume that there is some allowance being given for accepting whatever result you get in exchange for the money saved. There is no comparison between a properly done modern valve job, and anything done with a tapered pilot system. Also, if you're porting your own heads, your time has no value as again, it's all you for you. Basically, there are real reasons to spend and get high quality work if performance is the goal. And again, all around performance, not just horsepower. But if you need or want to save and sacrifice, just know going in that there is a difference.
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